Do not delete files related to gating on import
When `rhpkg import` is used, it will delete files that are not used
in the imported SRPM but are tracked in git. Now there is an exception
for 'gating.yaml' also 'tests/' subdirectory - these files are kept.
JIRA: COMPOSE-3672
Signed-off-by: Ondrej Nosek <onosek@redhat.com>