Updates of slaves to EL7

Updates of slaves to EL7

* Merge commonalities into the rackspace-convert-base script. That makes
the script more of a common setting bootstrap than just making sure
vagrant operates properly on a system but that's fine as it squashes
down our replication of code everywhere

* Update the configure_lf_infra script to accept a few more variables
and be more flexible

* Update the basic-builder to get rid of the common code that moved into
the rackspace-convert-base

* Update basic-java-node to get rid of the common code that moved into
the rackspace-convert-base. At present this effectively means that a
basic-java-node could be produced by just the rackspace-convert-base and
lf-networking vagrants as presently this vagrant is doing nothing but
making sure packages are up to date which the lf-networking vagrant also
does

Change-Id: I473a532dbd728d9829ac53fdbca2923a34b825e0
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>