Allow provisioners to overwrite the server given hostname for a
node, just like how they can set the ip addresses for a node.
Merge remote-tracking branch 'origin/develop' into feature/host-overwrite

Conflicts:
	server/src/test/java/com/continuuity/loom/http/LoomTaskHandlerTest.java
Merge pull request #438 from continuuity/feature/host-overwrite

Allow provisioners to overwrite the server given hostname for a