cifs: cifs_chan_is_iface_active should be called with chan_lock held

commit 7257bcf3 upstream.

cifs_chan_is_iface_active checks the channels of a session to see
if the associated iface is active. This should always happen
with chan_lock held. However, these two callers of this function
were missing this locking.

This change makes sure the function calls are protected with
proper locking.

Fixes: b54034a7 ("cifs: during reconnect, update interface if necessary")
Fixes: fa1d0508

 ("cifs: account for primary channel in the interface list")
Cc: stable@vger.kernel.org
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>