rsocket: Fix hang in rrecv() after disconnecting

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

Signed-off-by: Pradeep Satyanarayana <pradeeps@linux.vnet.ibm.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>