gitlab: use --refetch in check-patch/check-dco jobs

gitlab: use --refetch in check-patch/check-dco jobs

When gitlab initializes the repo checkout for a CI job, it will have
done a shallow clone with only partial history. Periodically the objects
that are omitted cause trouble with the check-patch/check-dco jobs. This
is exhibited as reporting strange errors being unable to fetch certain
objects that are known to exist.

Passing the --refetch flag to 'git fetch' causes it to not assume the
local checkout has all common objects and thus re-fetch everything that
is needed. This appears to solve the check-patch/check-dco job failures.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250225110525.2209854-1-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>