agent/proxy: address PR feedback

agent/proxy/daemon.go

@@ -284,6 +284,7 @@ func (p *Daemon) Stop() error {
 // used only for tests.
 func (p *Daemon) stopKeepAlive() error {
 	p.lock.Lock()
+	defer p.lock.Unlock()
 
 	// If we're already stopped or never started, then no problem.
 	if p.stopped || p.process == nil {
@@ -295,7 +296,6 @@ func (p *Daemon) stopKeepAlive() error {
 	// Note that we've stopped
 	p.stopped = true
 	close(p.stopCh)
-	p.lock.Unlock()
 
 	return nil
 }

agent/proxy/process_unix.go

@@ -22,9 +22,9 @@ func findProcess(pid int) (*os.Process, error) {
 	// a 0 signal. This will do nothing to the process but will still
 	// return errors if the process is gone.
 	err = p.Signal(syscall.Signal(0))
-	if err == nil || err == syscall.EPERM {
+	if err == nil {
 		return p, nil
 	}
 
-	return nil, fmt.Errorf("process is dead")
+	return nil, fmt.Errorf("process %d is dead or running as another user", pid)
 }