srm: clean up srmBringOnline implementation

Addresses SRM spec compliance issues.

Also updates the system-test test script to issue a bring-online
request and to work with Ruby 2.0 (warning: Ruby 2.0 may be required
now).

Target: trunk
Require-notes: no
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6142/