Add CHAP credentials support

Currently, the Hyper-V driver ignores the according CHAP
credentials when logging in iSCSI targets. For this reason,
attaching volumes fails when CHAP authentication is enforced.

This patch adds one way CHAP authentication support.

Change-Id: Id4d8800ae08dc24a01fc146f65c68b0b41d49e3d
Merge "Add CHAP credentials support"