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.

(cherry picked from commit 0309ba9480a6734f633241e9a5bd51bb8cacd0e1)

Change-Id: Id4d8800ae08dc24a01fc146f65c68b0b41d49e3d