Fix iSCSI DataStore is Connected But inaccessible

Remount a iSCSI datastore in ESXI host after network failure or
iSCSI DataStore is Connected But inaccessible 

:Scan volume
esxcfg-volume -l

[root@esxi-11:/vmfs/volumes] esxcfg-volume -l
Scanning for VMFS-6 host activity (4096 bytes/HB, 1024 HBs).
VMFS UUID/label: 5b9279dd-659af4f5-9f6c-1866daf4b576/QNAP-01:GRAYLOG
Can mount: Yes
Can resignature: Yes
Extent name: naa.6e843b61b1c7f97dd817d4d65d8bddd7:1     range: 0 - 8388351 (MB)
Extent name: naa.6e843b6ab3d267ad2373d43a8d9645da:1     range: 8388352 - 16776703 (MB)

Scanning for VMFS-6 host activity (4096 bytes/HB, 1024 HBs).
VMFS UUID/label: 5b91fa1a-8d4ad5f5-8747-1866daf3466e/QNAP-01:DS-01
Can mount: Yes
Can resignature: Yes
Extent name: naa.6e843b69306f933db3d1d4045da669da:1     range: 0 - 4194047 (MB)

:Mount Volume

esxcfg-volume -m QNAP-01:DS-01
esxcfg-volume -m QNAP-01:GRAYLOG