known-issues: fix regex to catch summary messages to ignore

The regular expression we use to catch the summary messages was not
generic enough to catch it. This causes it to not be classified as a
known issue to ignore and shows up in the output of
filter-known-issues, when it should not.

Fix the regex to be more generic.

Change-Id: I3e53d061325c90c861799dabc1f548177c650bc3
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>