* Fix lookup_passwordstore test skipping.
Skip all of RHEL instead of specific versions.
Skip all of CentOS < 7 instead of specific versions.
This makes the test more robust when testing newer versions.
Tests could be executed on RHEL if EPEL was installed during the test.
* [password] _random_password -> random_password and moved to util/encrypt.py
* [passwordstore] Use built-in random_password instead of pwgen utility
* [passwordstore] Add integration tests
