Tell user when waiting for sysroot lock

Currently, when a client asks the daemon to do something while something else has a lock on the sysroot, the daemon will sit & wait for the sysroot to unlock. In updatectl, this can manifest itself as a command that looks like it isn't doing anything (and, to be fair, that's exactly what's happening)

We should tell the user that we're waiting for the sysroot to become unlocked, and they can choose to abort the job with Ctrl+C