Use a new ruby 2.1 in the master node as a single ruby version

* remove unused gems;
* remove rbenv env;
* remove ruby compilation;
* use ruby 2.1 for master node.

TODO:
* remove raemon;
* remove build gems for Astute;
* update spec for Astute.

Change-Id: I099e65901ef3cf691f90d5bda4dd2f1a5cb76ea7
Implements: blueprint fuel-new-system-ruby-in-master-node