The connection request thread adds sockets to a select list unless

The connection request thread adds sockets to a select list unless
the cr->socket is invalid and the cr request state is set to destroy.  If the
cr->socket is invalid, but the cr->state is not destroy, then the cr->socket
is added to an FD set for select/poll.  This results in select/poll
returning an error when select is called.  As a result, the cr thread never
actually blocks during this state.

Fix this by only destroying a cr based on its state being set to destroy
and skip adding cr->sockets to the FD set when they are invalid.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>