Extract ISCSI tries option into connector module

The usage of this option occurred only in that module.
Rename this options to num_volume_device_scan_tries,
according to discussion on IRC.
The old one marked as depricated option.

DocImpact
Change-Id: Ib4a37237c2d95ca2dd6c05ce0a41f930b29ffd1c
Merge "Extract ISCSI tries option into connector module"