selftests/ftrace: Have reset_ftrace_filter handle modules

If a function probe in set_ftrace_filter belongs to a module, it will
contain the module name. Like:

 wmi_query_block [wmi]:traceoff:unlimited

But writing:

 '!wmi_query_block [wmi]:traceoff' > set_ftrace_filter

will cause an error. We still need to write:

 '!wmi_query_block:traceoff' > set_ftrace_filter

Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>