services/device/dmrun: Make dmrun work with the socket agent

Change-Id: I351912c3537da544b3bca7b0f9dd21ad086ad812
diff --git a/services/device/dmrun/dmrun.go b/services/device/dmrun/dmrun.go
index c829566..d816542 100644
--- a/services/device/dmrun/dmrun.go
+++ b/services/device/dmrun/dmrun.go
@@ -234,6 +234,10 @@
 		cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", ref.EnvCredentials, creds))
 	} else if agentCreds := os.Getenv(ref.EnvAgentEndpoint); len(agentCreds) > 0 {
 		cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", ref.EnvAgentEndpoint, agentCreds))
+	} else if agentCreds := os.Getenv(ref.EnvAgentPath); len(agentCreds) > 0 {
+		cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", ref.EnvAgentPath, agentCreds))
+	} else {
+		fmt.Fprintf(os.Stderr, "WARNING: no credentials found. You'll probably have authorization issues later on.\n")
 	}
 }