ktest: Run commands through list-form shell open

ktest: Run commands through list-form shell open

run_command() currently uses string-form open():

  open(CMD, "$command 2>&1 |")

That delegates parsing to the shell but also mixes the stderr redirection
into the command string. Switch to list-form open() with an explicit sh -c
wrapper so shell syntax errors are captured in the same output stream as
command output. Otherwise, important errors can not be retrieved from the
ktest LOG_FILE.

Cc: John Hawley <warthog9@eaglescrag.net>
Cc: Andrea Righi <arighi@nvidia.com>
Cc: Marcos Paulo de Souza <mpdesouza@suse.com>
Cc: Matthieu Baerts <matttbe@kernel.org>
Cc: Fernando Fernandez Mancera <fmancera@suse.de>
Cc: Pedro Falcato <pfalcato@suse.de>
Link: https://patch.msgid.link/20260307-ktest-fixes-v1-5-565d412f4925@suse.com
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>