Merge pull request #1093 from dimitern/lp-1359714-juju-machine-id-for-charms

Fixed lp:1359714: JUJU_MACHINE_ID added to hook context

JUJU_MACHINE_ID is now available to charm hooks. It contains
the unit's assigned machine ID.
Merge pull request #1121 from wallyworld/backport-lp-1359714

Merge pull request #1093 from dimitern/lp-1359714-juju-machine-id-for-charms

Fixed lp:1359714: JUJU_MACHINE_ID added to hook context

JUJU_MACHINE_ID is now available to charm hooks. It contains
the unit's assigned machine ID.