fsnotify: replace igrab() with ihold() on attach connector

We must have a reference on inode, so ihold is cheaper.

Link: https://lore.kernel.org/r/20210810151220.285179-2-amir73il@gmail.com


Reviewed-by: Matthew Bobrowski <repnop@google.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>