ftrace/selftest: Fix reset_trigger() to handle triggers with filters

ftrace/selftest: Fix reset_trigger() to handle triggers with filters

The reset_trigger() function breaks up the command by a space ' '. This is
useful to ignore the '[active]' word for triggers when removing them. But if
the trigger has a filter (ie. "if prio < 10") then the filter needs to be
attached to the line that is written into the trigger file to remove it. But
the truncation removes the filter and the triggers are not cleared properly.

Before, reset_trigger() did this:

 # echo 'hist:keys=common_pid if prev_prio < 10' > events/sched/sched_switch/trigger
 # echo 'hist:keys=common_pid if next_prio < 10' >> events/sched/sched_switch/trigger
 # cat events/sched/sched_switch/trigger
hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if prev_prio < 10 [active]
hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if next_prio < 10 [active]

 reset_trigger() {
   echo '!hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048' >> events/sched/sched_switch/trigger
 }

 # cat events/sched/sched_switch/trigger
hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if prev_prio < 10 [active]
hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if next_prio < 10 [active]

After, where it includes the filter:

 reset_trigger() {
   echo '!hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if prev_prio < 10' >> events/sched/sched_switch/trigger
 }

 # cat events/sched/sched_switch/trigger
hist:keys=common_pid:vals=hitcount:sort=hitcount:size=2048 if next_prio < 10 [active]

Fixes: ec1e6363b22f0 ("kselftests/ftrace : Add event trigger testcases")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>