SUNRPC fix regression in umount of a secure mount

If call_status returns ENOTCONN, we need to re-establish the connection
state after. Otherwise the client goes into an infinite loop of call_encode,
call_transmit, call_status (ENOTCONN), call_encode.

Fixes: c8485e4d ("SUNRPC: Handle ECONNREFUSED correctly in xprt_transmit()")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Cc: stable@vger.kernel.org # v2.6.29+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>