Add vmedia boot support for deploy-ironic element

deploy-ironic element currently retrieves token over tftp and
expects BOOT_IP_ADDRESS to be set.  This commit adds support for
retrieving token file from virtual media if node booted from
virtual media. Also corrects the issue for BOOT_IP_ADDRESS not set
for virtual media boot.

Change-Id: I3d5f1779b9b17842360860c7778baa01db1e1a52
Closes-Bug: #1356339
Reset yum configuration in post-install.d

When using the yum element, we should reset the changes we've made to
/etc/yum.conf during post-install.d. Otherwise, this build time
configuration is propagated into booted instances.

Change-Id: I1eea586ca0fefe9bc0cf91fedefcbd141a536fa2
Run environment.d hook for manifests earlier

15-pip-manifests depends on the variables defined by the manifests
element, so we need to run this one earlier. I would have thought things
were alpha sorted after the numerical sort...but I just ran into this,
so apparently not.

Change-Id: Ifedf544222b5a8eb7630efda609eb6a5b9629de3
Merge "Add vmedia boot support for deploy-ironic element"
Merge "Run environment.d hook for manifests earlier"
Merge "Reset yum configuration in post-install.d"