core: attach sd  - avoid failover in case of export domain

When attaching an export storage domain and having a failure which
isn't spm/master domain related, avoid failover.

Change-Id: Iea8ae06d5327e46b5cdb7ed73239744a1ba6ffc3
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=896484
Signed-off-by: Liron Aravot <laravot@redhat.com>