perf test trace: Remove set -e and print trace test's error messages

perf test trace: Remove set -e and print trace test's error messages

Currently perf test utilizes the set -e option in shell that exit
immediately if a command exits with a non-zero status, this prevents
further error handling and introduces ambiguity. This patch removes set
-e and prints the error message after invoking perf trace during perf
tests.

In my case, the command that exits with a non-zero status is perf
trace instead of grep, because it can't find the 'timer:hrtimer_setup'
tracepoint, see below.

Before:
    $ sudo /tmp/perf test enum -vv
    107: perf trace enum augmentation tests:
    107: perf trace enum augmentation tests                              : Running
    --- start ---
    test child forked, pid 783533
    Checking if vmlinux exists
    Tracing syscall landlock_add_rule
    Tracing non-syscall tracepoint syscall
    ---- end(-1) ----
    107: perf trace enum augmentation tests                              : FAILED!

After:
    $ sudo /tmp/perf test enum -vv
    107: perf trace enum augmentation tests:
    107: perf trace enum augmentation tests                              : Running
    --- start ---
    test child forked, pid 851658
    Checking if vmlinux exists
    Tracing syscall landlock_add_rule
    Tracing non-syscall tracepoint timer:hrtimer_setup,timer:hrtimer_start
    [tracepoint failure] Failed to trace tracepoint timer:hrtimer_setup,timer:hrtimer_start, output:
    event syntax error: 'timer:hrtimer_setup,timer:hrtimer_start'
			 \___ unknown tracepoint

    Error:  File /sys/kernel/tracing//events/timer/hrtimer_setup not found.
    Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

    Run 'perf list' for a list of valid events

     Usage: perf trace [<options>] [<command>]
	or: perf trace [<options>] -- <command> [<options>]
	or: perf trace record [<options>] [<command>]
	or: perf trace record [<options>] -- <command> [<options>]

	-e, --event <event>   event/syscall selector. use 'perf list' to list available events---- end(-1) ----
    107: perf trace enum augmentation tests                              : FAILED!

Signed-off-by: Howard Chu <howardchu95@gmail.com>
Tested-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250528191148.89118-3-howardchu95@gmail.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>