If you try to resize a lvol to the current size return a changed=False and don't fail.

This addresses GH-5165 and adds the ability to check if a lvol exists.

The tests for this don't fit nicely into the current integration tests so they are below.

```
---

- name: remove any existing lv=one of vg=main
  lvol: lv=one vg=main state=absent

- name: remove any existing lv=two of vg=main
  lvol: lv=two vg=main state=absent

- name: check to see if lv=one of vg=main exists
  lvol: lv=one vg=main state=present
  ignore_errors: true
  register: lvol_result0

- name: Assert that we will get a "No size given."
  assert:
    that:
      - "'No size given.' in lvol_result0.msg"

- name: create lv=one of vg=main sized 30g
  lvol: lv=one size=30g vg=main state=present
  register: lvol_result1

- name: Assert that we made changes."
  assert:
    that:
      - "lvol_result1.changed == True"

- name: check to see if lv=one of vg=main exists
  lvol: lv=one vg=main state=present
  register: lvol_result2

- name: Assert that we did not make changes."
  assert:
    that:
      - "lvol_result2.changed == False"

- name: remove lv=one of vg=main
  lvol: lv=one vg=main state=absent

- name: create lv=two of vg=main sized 30G
  lvol: lv=two size=30G vg=main state=present
  register: lvol_result3

- name: Assert that we made changes."
  assert:
    that:
      - "lvol_result3.changed == True"

- name: reduce lv=two of vg=main to 15G
  lvol: lv=two size=15G vg=main state=present
  register: lvol_result4

- name: Assert that we made changes."
  assert:
    that:
      - "lvol_result4.changed == True"

- name: increase lv=two of vg=main to 30G
  lvol: lv=two size=30G vg=main state=present
  register: lvol_result5

- name: Assert that we made changes."
  assert:
    that:
      - "lvol_result5.changed == True"

- name: create lv=two of vg=main sized 30G when already exists at 30G
  lvol: lv=two size=30g vg=main state=present
  register: lvol_result6

- name: Assert that we did not make changes."
  assert:
    that:
      - "lvol_result6.changed == False"

- name: remove lv=two of vg=main
  lvol: lv=two vg=main state=absent
```

library/system/lvol

@@ -72,8 +72,10 @@ EXAMPLES = '''
 '''
 
 import re
+
 decimal_point = re.compile(r"(\.|,)")
 
+
 def parse_lvs(data):
     lvs = []
     for line in data.splitlines():
@@ -84,6 +86,7 @@ def parse_lvs(data):
         })
     return lvs
 
+
 def main():
     module = AnsibleModule(
         argument_spec=dict(
@@ -102,9 +105,6 @@ def main():
     size_opt = 'L'
     size_unit = 'm'
 
-    if state=='present' and not size:
-        module.fail_json(msg="No size given.")
-
     if size:
         # LVCREATE(8) -l --extents option with percentage
         if '%' in size:
@@ -141,7 +141,9 @@ def main():
         unit = 'm'
     else:
         unit = size_unit
-    rc,current_lvs,err = module.run_command("lvs --noheadings -o lv_name,size --units %s --separator ';' %s" % (unit, vg))
+
+    rc, current_lvs, err = module.run_command(
+        "lvs --noheadings -o lv_name,size --units %s --separator ';' %s" % (unit, vg))
 
     if rc != 0:
         if state == 'absent':
@@ -160,6 +162,12 @@ def main():
     else:
         this_lv = None
 
+    if state == 'present' and not size:
+        if this_lv is None:
+            module.fail_json(msg="No size given.")
+        else:
+            module.exit_json(changed=False, vg=vg, lv=this_lv['name'], size=this_lv['size'])
+
     msg = ''
     if this_lv is None:
         if state == 'present':
@@ -200,6 +208,8 @@ def main():
                     rc, _, err = module.run_command("%s -%s %s%s %s/%s" % (tool, size_opt, size, size_unit, vg, this_lv['name']))
                     if rc == 0:
                         changed = True
+                    elif "matches existing size" in err:
+                        module.exit_json(changed=False, vg=vg, lv=this_lv['name'], size=this_lv['size'])
                     else:
                         module.fail_json(msg="Unable to resize %s to %s%s" % (lv, size, size_unit), rc=rc, err=err)
 
@@ -207,4 +217,5 @@ def main():
 
 # import module snippets
 from ansible.module_utils.basic import *
+
 main()