CP-4431: Tweak description of message_removed error

I think the new version make a little more then when using the CLI.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
CP-4431: Remove VMPP CLI commands

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
CP-4431: Mark VMPR stuff as "removed" in API docs

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>