Fix bug ansible#5328 apache module loading

Currently, the apache2_module module parses apache configs
for correctness when enabling or disabling apache2 modules.

This behavior introduced a conflict condition when transitioning
between certain modules, such as mpm_worker and mpm_event.

This change only parses apache's configs during check mode,
otherwise it parses the stdout results of attempted to enabled
or disable modules to determine change state.

web_infrastructure/apache2_module.py

@@ -103,26 +103,25 @@ def _set_state(module, state):
     a2mod_binary = {'present': 'a2enmod', 'absent': 'a2dismod'}[state]
     success_msg = "Module %s %s" % (name, state_string)
 
-    if _module_is_enabled(module) != want_enabled:
-        if module.check_mode:
-            module.exit_json(changed = True, result = success_msg)
+    if module.check_mode:
+        module.exit_json(changed = _module_is_enabled(module) != want_enabled, result = success_msg)
 
-        a2mod_binary = module.get_bin_path(a2mod_binary)
-        if a2mod_binary is None:
-            module.fail_json(msg="%s not found. Perhaps this system does not use %s to manage apache" % (a2mod_binary, a2mod_binary))
+    a2mod_binary = module.get_bin_path(a2mod_binary)
+    if a2mod_binary is None:
+        module.fail_json(msg="%s not found. Perhaps this system does not use %s to manage apache" % (a2mod_binary, a2mod_binary))
 
-        if not want_enabled and force:
-            # force exists only for a2dismod on debian
-            a2mod_binary += ' -f'
+    if not want_enabled and force:
+        # force exists only for a2dismod on debian
+        a2mod_binary += ' -f'
 
-        result, stdout, stderr = module.run_command("%s %s" % (a2mod_binary, name))
+    result, stdout, stderr = module.run_command("%s %s" % (a2mod_binary, name))
 
-        if _module_is_enabled(module) == want_enabled:
-            module.exit_json(changed = True, result = success_msg)
-        else:
-            module.fail_json(msg="Failed to set module %s to %s: %s" % (name, state_string, stdout), rc=result, stdout=stdout, stderr=stderr)
-    else:
+    if result != 0:
+        module.fail_json(msg="Failed to set module %s to %s: %s" % (name, state_string, stdout), rc=result, stdout=stdout, stderr=stderr)
+    elif re.match(r'.*(already (disabled|enabled|present)|not present)', stdout, re.S):
         module.exit_json(changed = False, result = success_msg)
+    else:
+        module.exit_json(changed = True, result = success_msg)
 
 def main():
     module = AnsibleModule(