[dcpdrain] Check the status for DcpStreamReq

The user may not have access to stream the given
scope causing StreamReq to fail with "no access".
Previously this would cause dcpdrain to "hang" forever
sending DCP no-ops to the server.

Change-Id: I7b30835874518659625eab361b94e880fbf3bf2c
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/176965
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Richard de Mellow <richard.demellow@couchbase.com>

programs/dcpdrain/dcpdrain.cc

@@ -303,7 +303,22 @@ class DcpConnection {
     }
 
     void handleResponse(const cb::mcbp::Response& response) {
-        // Do nothing
+        if (cb::mcbp::isStatusSuccess(response.getStatus())) {
+            return;
+        }
+
+        if (response.getClientOpcode() ==
+            cb::mcbp::ClientOpcode::DcpStreamReq) {
+            std::cerr << TerminalColor::Red << response.toJSON(true).dump()
+                      << TerminalColor::Reset << std::endl;
+            stream_end++;
+            if (stream_end == vbuckets.size()) {
+                // we got all we wanted
+                connection->getUnderlyingAsyncSocket().setReadCB(nullptr);
+                connection->getUnderlyingAsyncSocket().close();
+                stop = std::chrono::steady_clock::now();
+            }
+        }
     }
 
     void handleDcpNoop(const cb::mcbp::Request& header) {