SUNRPC: Fix a thinko in xs_connect()

It is rather pointless to test the value of transport->inet after
calling xs_reset_transport(), since it will always be zero, and
so we will never see any exponential back off behaviour.
Also don't force early connections for SOFTCONN tasks. If the server
disconnects us, we should respect the exponential backoff.

Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>