Update various modules for check_mode

This updates the following modules to support check_mode:
* apt_key
* apt_repository
* easy_install
* pip - will always report changed due to the way it handles state
* seboolean
* selinux
* slurp - since nothing changes, it just adds that it supports
  check_mode
* subversion - reports changed when checking out new repo and
  when updating.
* supervisorctl
* svr4pkg

See issue #2114.

library/seboolean

@@ -160,7 +160,8 @@ def main():
             name=dict(required=True),
             persistent=dict(default='no', type='bool'),
             state=dict(required=True, type='bool')
-        )
+        ),
+        supports_check_mode=True
     )
 
     if not HAVE_SELINUX:
@@ -188,6 +189,8 @@ def main():
         result['changed'] = False
         module.exit_json(**result)
 
+    if module.check_mode:
+        module.exit_json(changed=True)
     if persistent:
         r = semanage_boolean_value(module, name, state)
     else: