Updates root-enable & root-show help messages

Reasons:
- Help message for root-enable does not gives complete information, it
  misses that API also resets root, on existence.
- Current help message for root-show makes it feel like current status
  of root user is fetched, but instead we are also returning True for
  historical root access enabled.

Changes:
- Updated the root-enable and root-show API help message.
- Updated README for updated help messages.

Change-Id: Ide7c331bdfe5437e6966f6cd4f331cb3b22d0c3f
Closes-Bug: #1277308

README.rst

@@ -120,8 +120,8 @@ You'll find complete documentation on the shell by running
          resize-flavor       Resizes the flavor of an instance.
          resize-volume       Resizes the volume size of an instance.
          restart             Restarts an instance.
-         root-enable         Enables root for an instance.
-         root-show           Shows 'root enabled' status of an instance.
+         root-enable         Enables root for an instance and resets if already exists.
+         root-show           Gets status if root was ever enabled for an instance.
          secgroup-add-rule   Creates a security group rule.
          secgroup-delete-rule
                              Deletes a security group rule.

troveclient/v1/shell.py

@@ -548,7 +548,7 @@ def do_limit_list(cs, args):
 @utils.arg('instance', metavar='<instance>', help='ID of the instance.')
 @utils.service_type('database')
 def do_root_enable(cs, args):
-    """Enables root for an instance."""
+    """Enables root for an instance and resets if already exists."""
     root = cs.root.create(args.instance)
     utils.print_dict({'name': root[0], 'password': root[1]})
 
@@ -556,7 +556,7 @@ def do_root_enable(cs, args):
 @utils.arg('instance', metavar='<instance>', help='ID of the instance.')
 @utils.service_type('database')
 def do_root_show(cs, args):
-    """Shows 'root enabled' status of an instance."""
+    """Gets status if root was ever enabled for an instance."""
     root = cs.root.is_root_enabled(args.instance)
     utils.print_dict({'is_root_enabled': root.rootEnabled})