NFS: Don't recoalesce on error in nfs_pageio_complete_mirror()

NFS: Don't recoalesce on error in nfs_pageio_complete_mirror()

BugLink: https://bugs.launchpad.net/bugs/1837952
commit 8127d82705998568b52ac724e28e00941538083d upstream.

If the I/O completion failed with a fatal error, then we should just
exit nfs_pageio_complete_mirror() rather than try to recoalesce.

Fixes: a7d42ddb3099 ("nfs: add mirroring support to pgio layer")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>