pkgset: ignore events for modular content tags
    
    Generally we want all packages to come from particular event.
    
    There are two exceptions: packages configured via `pkgset_koji_builds`
    are pulled in by exact NVR and skip event; and modules in
    `pkgset_koji_modules` are pulled in by NSVC and also ignore events.
    
    However, the modular content tag did honor event, and could lead to a
    crashed compose if the content tag did not exist at the configured
    event.
    
    This patch is a slightly too big hammer. It ignores events for all
    modules, not just ones configured by explicit NSVC. It's not a huge deal
    as the content tags are created before the corresponding module build is
    created, and once all rpm builds are tagged into the content tag, MBS
    will never change it again.
    
    JIRA: RHELCMP-12765
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>