UBUNTU: SAUCE: (namespace) userns: Export current_in_userns to modules

BugLink: http://bugs.launchpad.net/bugs/1617550

Building fuse as a module fails because this symbol is not
exported.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>

kernel/user_namespace.c

@@ -964,6 +964,7 @@ bool current_in_userns(const struct user_namespace *target_ns)
 	}
 	return false;
 }
+EXPORT_SYMBOL(current_in_userns);
 
 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
 {