rsocket: Fix hang in rrecv/rsend after disconnecting

rsocket: Fix hang in rrecv/rsend after disconnecting

If a user calls rrecv() after a blocking rsocket has been disconnected,
it will hang.  This problem and the cause was reported by Sirdhar Samudrala
<samudrala@us.ibm.com>.  It can be reproduced by running netserver -f -D
using the rs-preload library.  A similar issue exists with rsend().

Fix this by not blocking on a CQ unless we're connected.

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