testlib.py: Add gensnippet_if crash to allowed_messages (#14690)
testlib.py: Add gensnippet_if crash to allowed_messages (#14690)

See https://bugzilla.redhat.com/show_bug.cgi?id=1884236.

Closes #14690
deryni/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,mvollmer/cockpit,garrett/cockpit,cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,deryni/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,garrett/cockpit