Fix data race in the shim

A data race existed between reading and setting the error value returned
from stream.Recv(). Modify the shim to avoid the race and add a bit more
alignment between the peer and shim stream processing functions.

Fix data races in MockCCComm

- Quit was causing a race between channel send and close. Resolved by
  wiring a channel to Run and closing send and receive after the done
  channel had closed.
- The keep alive go routine was racing on the keepAlive message during
  send. Wired the done channel into the keep-alive go routine.
- Some tests are setting responses while go routines are running. Work
  around this bad behavior with a lock to avoid restructuring tests.

Change-Id: I49bab82336bbbeb941b7db2d8bd279f254b4ec9f
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>