xprtrdma: Use re_connect_status safely in rpcrdma_xprt_connect()

Clean up: Sometimes creating a fresh rpcrdma_ep can fail. That's why
xprt_rdma_connect() always checks if the r_xprt->rx_ep pointer is
valid before dereferencing it. Instead, xprt_rdma_connect() can
simply check rpcrdma_xprt_connect()'s return value.

Also, there's no need to set re_connect_status to zero just after
the rpcrdma_ep is created, since it is allocated with kzalloc.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>