ovirt: Improve handling of g_strv_contains()
    
    The ovirt code uses g_strv_contains() with fallback code in
    glib-compat.h when we are using a glib version where it's not available.
    However, when we use a glib version where g_strv_contains is available,
    we get a compilation warning since we are compiling GLIB_VERSION_MAX_ALLOWED
    set to 2.38.
    
    This commit wraps both the compat code and the g_strv_contains() call in
    a strv_contains() helper where we can hide the magic needed to avoid
    deprecation warnings.
    
    Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>
    Acked-by: Eduardo Lima (Etrunko) <etrunko@redhat.com>