selftests: tracing: Use mutex_unlock for testing glob filter

Since commit c5b6abab ("locking/mutex: implement
mutex_trylock_nested") makes mutex_trylock() as an inlined
function if CONFIG_DEBUG_LOCK_ALLOC=y, we can not use
mutex_trylock() for testing the glob filter of ftrace.

Use mutex_unlock instead.

Link: https://lore.kernel.org/r/175151680309.2149615.9795104805153538717.stgit@mhiramat.tok.corp.google.com


Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>