Turns off ambari and hadoop2 services for initial VM boot in HDP images

This patch resolves a minor bug in the HDP image generation scripts.

Some warning and error messages show up in the boot.log for VM
  instances based on the HDP images (v1.3.2 and v2.0.6).  The
  warnings involve the ambari-server startup, as well as the
  startup of some Hadoop 2 services in the v2.0.6 image.

The basic problem is that these services should not be starting
  upon the first boot of the image, since the HDP plugin has
  not yet configured the VM instances for a cluster startup.

The ambari-server and ambari-agent services have been turned off
  by default in this patch, by using the chkconfig command.  This keeps
  the ambari services from starting at first boot. This is desired,
  since the Ambari services don't have the configuration required
  during initial boot to function properly.

The same issue occurs with the Hadoop 2 services, and these are
  turned off using the same chkconfig mechanism.

Closes-Bug: #1317270

Change-Id: I5fdd45a41b2e6bb8f9b632594bbd6ee538e09512