Revert "runner: check disk limit at dumping kmsg"

This reverts commit 3bd8bf9b.

After some tests it seems that runner is not reporting failures
properly from i915_selftest due to this change, also after
re-thinking I come to conclusion that clipping may be applied
after runner/resume processes a tests dmesg from a run into
rusults.json

Fixes: 3bd8bf9b ("runner: check disk limit at dumping kmsg")
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Petri Latvala <adrinael@adrinael.net>
Signed-off-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>