There's an issue during NID replacement at the customer site. With thousands of clients, unmounting all connections is difficult. When the MGS starts with the nosvc option, some clients reconnect, preventing the replace_nid operation from completing. Let's introduce a new mount option "noclient" to block all non-local connections for MGS, allowing replace_nid to succeed.

.....mgs_replace_nids()) Only MGS is allowed to be started
.....mgs_iocontrol()) MGS: error replacing nids: rc = -115