Work around a bug in systemd by always setting fsname.

See bazil/fuse#89 for more details.

mounted_file_system.go

@@ -114,9 +114,23 @@ func (c *MountConfig) bazilfuseOptions() (opts []bazilfuse.MountOption) {
 	// InodeAttributes.Mode.
 	opts = append(opts, bazilfuse.SetOption("default_permissions", ""))
 
+	// HACK(jacobsa): Work around what appears to be a bug in systemd v219, as
+	// shipped in Ubuntu 15.04, where it automatically unmounts any file system
+	// that doesn't set an explicit name.
+	//
+	// When Ubuntu contains systemd v220, this workaround should be removed and
+	// the systemd bug reopened if the problem persists.
+	//
+	// Cf. https://github.com/bazil/fuse/issues/89
+	// Cf. https://bugs.freedesktop.org/show_bug.cgi?id=90907
+	fsname := c.FSName
+	if runtime.GOOS == "linux" && fsname == "" {
+		fsname = "some_fuse_file_system"
+	}
+
 	// Special file system name?
-	if c.FSName != "" {
-		opts = append(opts, bazilfuse.FSName(c.FSName))
+	if fsname != "" {
+		opts = append(opts, bazilfuse.FSName(fsname))
 	}
 
 	// Read only?