Description of problem:

"Failed to determine the metadata devices of Storage Domain" is shown for every storage domain in the event panel in a 4.1 environment which is having hosts with vdsm version less than 4.19.x.

The "StorageDomain.getInfo" will return "vgMetadataDevice" and "metadataDevice" only from vdsm 4.19.x. The 4.18.x will not report these values as seen below.

===
jsonrpc.Executor/5::DEBUG::2018-02-05 17:56:42,685::__init__::555::jsonrpc.JsonRpcServer::(_handle_request) Return 'StorageDomain.getInfo' in bridge with {'uuid': 'ad063d42-ba9e-4515-929d-3f6dd0c12628', 'vguuid': 'X7CUCg-yFp6-juim-4WUZ-ROFV-3sRd-GKsAWz', 'state': 'OK', 'version': '3', 'role': 'Master', 'type': 'ISCSI', 'class': 'Data', 'pool': ['dae2555d-f30e-4660-8581-63cc16474d5d'], 'name': 'test_storage'}
===

As per the https://gerrit.ovirt.org/#/c/77085/, the engine will give error mentioned above if either vgMetadataDevice or metadataDevice are null. Since vdsm doesn't return any values for these variables, we will get the error below in the engine log and the events panel.

===
2018-02-05 07:26:42,333-05 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.HSMGetStorageDomainInfoVDSCommand] (org.ovirt.thread.pool-6-thread-11) [2c9783ac] START, HSMGetStorageDomainInfoVDSCommand(HostName = 10.74.130.111, HSMGetStorageDomainInfoVDSCommandParameters:{runAsync='true', hostId='dba8d52f-1524-4f6c-8e30-0115de2990a4', storageDomainId='92227e03-01c8-4f41-999e-032175f20116'}), log id: 7c3b7ca1

2018-02-05 07:26:42,336-05 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.HSMGetStorageDomainInfoVDSCommand] (org.ovirt.thread.pool-6-thread-10) [22fc14b7] FINISH, HSMGetStorageDomainInfoVDSCommand, return: <StorageDomainStatic:{name='test_storage', id='ad063d42-ba9e-4515-929d-3f6dd0c12628'}, dae2555d-f30e-4660-8581-63cc16474d5d>, log id: 79e9e79f

2018-02-05 07:26:42,366-05 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (org.ovirt.thread.pool-6-thread-10) [22fc14b7] EVENT_ID: FAILED_DETERMINE_STORAGE_DOMAIN_METADATA_DEVICES(1,219), Correlation ID: null, Call Stack: null, Custom ID: null, Custom Event ID: -1, Message: Failed to determine the metadata devices of Storage Domain test_storage.
===

However, the storage domain is having the correct metadata.

===
pvs -o +pv_mda_free,pv_mda_count,pv_mda_used_count
  PV                                            VG                                   Fmt  Attr PSize  PFree  PMdaFree  #PMda #PMdaUse
  /dev/mapper/360014053f404fa44d844d9198cfee437 92227e03-01c8-4f41-999e-032175f20116 lvm2 a--  48.62g 42.38g        0      2        2
===


Version-Release number of selected component (if applicable):

vdsm 4.18.x
rhevm-4.1.8.2-0.1.el7.noarch


How reproducible:

100%

Steps to Reproduce:

1. Add 4.0 hosts in a 4.1 environment. The error will be shown every time when you activate the storage domain or restart the ovirt-engine service.


Actual results:

Incorrect error in the events panel of RHV-M with older vdsm version.