Add ctrl-c signal handler to loopback for graceful unmount

Signed-off-by: Alex Fishman <alex@fuse-t.org>
Change-Id: I82de5e2dd0340da4e05e4ccf1bbd162dff33b656

example/loopback/main.go

@@ -127,5 +127,13 @@ func main() {
 	if !*quiet {
 		fmt.Println("Mounted!")
 	}
+
+	c := make(chan os.Signal)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-c
+		server.Unmount()
+	}()
+
 	server.Wait()
 }