IB/srp: Avoid sending a task management function needlessly

commit 3780d1f0 upstream.

Do not send a task management function if sending will fail anyway
because either there is no RDMA/RC connection or the QP is in the
error state.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dave@thedillows.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>