Fix mis-named local (logging -> logging_config)

This only adds only the test for the situation when the file is defined in the
config. I'd prefer to test the other case but RSpec isn't playing nicely since
we also configure the logger in the RSpec configuration. For some reason it
fails to meet the expectation when the third argument, the layout, is replaced
with the 'anything' matcher.
Update bosh release ruby to 2.1.4

Fixes CVE-2014-8080[0] and CVE-2014-4975[1].

[0] Denial of Service XML Expansion
https://www.ruby-lang.org/en/news/2014/10/27/rexml-dos-cve-2014-8080/

[1] segmentation fault/buffer overrun in pack.c (encodes)
http://people.canonical.com/~ubuntu-security/cve/2014/CVE-2014-4975.html