Optimize clone checkout

Break out clone and checkout repositories into their own commands.
Modified existing install-geard, build-geard, build-geard-broker commands to no longer perform clone and checkout.

Jenkins job should be updated as follows:
...
vagrant up --provider aws
vagrant clone-upstream-repos --clean
vagrant checkout-repos --branch next_gen_node
vagrant install-geard
vagrant build-geard
vagrant build-geard-broker
...