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
Sync server_external_events v2 to v2.1 Part 1

This syncs commit I18062b81e50c722ec96b4296ac39384493683ae3 which
was made to the v2 version of os-server-external-events but not
the v2.1 version.

Partially implements blueprint v2-on-v3-api

Change-Id: If0657744fac021f635ce292142c82239751ae2f2
Sync server_external_events v2 to v2.1 Part 2

This syncs commit 5e4a5f0d8c62ca6e94ae6db16e9fbe0428805158 which
was made to the v2 version of os-server-external-events but not
the v2.1 version.

Partially implements blueprint v2-on-v3-api

Change-Id: I458b28b1f3cf161b6d40ce3fd8b3a9c5d090bde7
Merge "Add CHAP credentials support"
Merge "Sync server_external_events v2 to v2.1 Part 1"
Merge "Sync server_external_events v2 to v2.1 Part 2"