ktest: Resolve LOG_FILE in test option context

ktest: Resolve LOG_FILE in test option context

LOG_FILE is expanded immediately after the config file is parsed with
eval_option(..., -1). That uses the default context, not the same option
resolution path used for tests. If LOG_FILE depends on options that are
finalized per test, it can be resolved from stale values before the first
test starts.

Resolve LOG_FILE through set_test_option("LOG_FILE", 1) instead so it uses
the same expansion rules as the rest of the test options.

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-v1-2-565d412f4925@suse.com
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>