for plugins, store variables in /etc/default/ovirt

Store kernel commandline arguments for plugins in /etc/default/ovirt
This allows a system like puppet to be used to pre-seed the variables
rather than reading /proc/cmdline directly.

Change-Id: I7da94b3f8f0ea2d6f9abe8514a49cc5dc73c429b
Signed-off-by: Mike Burns <mburns@redhat.com>