module(nagios): don't catch SystemExit

If we do this, we risk outputting two JSON payloads, which will be
unparsable.

monitoring/nagios

@@ -214,7 +214,7 @@ def main():
             m = int(minutes)
             if not isinstance(m, types.IntType):
                 module.fail_json(msg='minutes must be a number')
-        except:
+        except Exception:
             module.fail_json(msg='invalid entry for minutes')
 
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