Medium: IPaddr2/findif.sh: Do a sanity check only on start and validate-all

monitor should not return OCF_ERR_CONFIGURED on an actual failure
even if a NIC is disappeared otherwise the whole resources stop.
ref:
  https://github.com/ClusterLabs/resource-agents/issues/328
Dev: IPaddr2/findif.sh: Add a test case for a monitor failure
Merge pull request #334 from kskmori/ipaddr2-ifcheck-when-start

 Medium: IPaddr2/findif.sh: Do a sanity check only on start and validate-all