nfs: update inode ctime after removexattr operation

nfs: update inode ctime after removexattr operation

xfstest generic/728 fails with delegated timestamps. The client does a
removexattr and then a stat to test the ctime, which doesn't change. The
stat() doesn't trigger a GETATTR because of the delegated timestamps, so
it relies on the cached ctime, which is wrong.

The setxattr compound has a trailing GETATTR, which ensures that its
ctime gets updated. Follow the same strategy with removexattr.

Fixes: 3e1f02123fba ("NFSv4.2: add client side XDR handling for extended attributes")
Reported-by: Olga Kornievskaia <aglo@umich.edu>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>