xio: fix for xio_msg release after teardown

xio: fix for xio_msg release after teardown

The xio_msg pointers to be freed in XioPortal::release_xio_rsp() are no
longer valid after a call to xio_connection_destroy(). We were already
avoiding the call to xio_release_msg() in this case, but were still
dereferencing the xio_msg for its user_context pointer. Moved the check
for is_connected() outside of the loop to avoid any access to msg.

Suggested-by: Vu Pham <vuhuong@mellanox.com>
Signed-off-by: Casey Bodley <casey@cohortfs.com>