pmgqm: warn if not running on master

pmgqm: warn if not running on master

pmgqm should exit when running on a non-master node (instead of e.g. sending
out spam report mails multiple times).
However this condition should not be an error - a warning printed should
suffice.

changing the die to warn + return in the calls for 'status' and 'send'
achieves this effect.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Reviewed-By: Dominik Csapak <d.csapak@proxmox.com>