qemuMigrationSrcIsSafe: Check local storage more thoroughly
https://bugzilla.redhat.com/show_bug.cgi?id=1494454
If a domain disk is stored on local filesystem (e.g. ext4) but is
not being migrated it is very likely that domain is not able to
run on destination. Regardless of share/cache mode.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>