In go, a context is an object that carries cancellation signals across
API boundaries. In fabric, contexts are associated with gRPC requests
and get propagated through the system. When a request to invoke
chaincode is received, the context is propagated to the controller
responsible for managing container requests where it is misused.

The controller spawns a go routine to handle the container request and
signals completion via a channel. The Process function then waits for
the request to complete or for the context to get canceled. When the
context it canceled, the processor still waits for the request to
complete before returning to the caller. This means the operation is
never really canceled at this layer and, since it has to complete,
it's likely that it has succeeded.

Unfortunately, once the context is canceled, the controller returns the
cancellation error from the context causing the callers to treat the
operation as a failure.

As the code downstream of the controller doesn't properly honor the
context either and future releases remove it entirely, we'll simply
ignore context cancellation signals in the controller.

Change-Id: I51d8be9ef41e586c982abe268e6f9e0d61d4d7a7
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>