cmdlib: Fix issue when marking node as online

When a node is marked as online (“gnt-node modify -O no …”), an RPC is
made to the node to check whether the node daemon is running. My recent
RPC changes led to offline nodes being ignored before the actual call is
made, thereby causing this check to fail. This is a workaround and needs
to be cleaned up later.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Signed-off-by: Andrea Spadaccini <spadaccio@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>