[v6r12] Av140512-v6r12: to deal with Disk/Tape separation

[avedaee]

Ref. on JIRA: https://its.cern.ch/jira/browse/LHCBDIRAC-261?filter=-1

In order to deal with the Disk/Tape separation I made a small change in
DowntimeCommand, ResourceManagementClient and ResourceManagementDB

2 more remarks:

1. we need an additional field "gocdbServiceType" in the DowntimeCache table inside the corresponding RM DB to store 2 service types ("srm" or "srm.nearline")
2. DowntimeCommand is using a getStorageElementOptions method in DIRAC.ConfigurationSystem.Client.Helpers.Resources and this might be changed soon

[fstagni]

From a pure code point of view this seems ok, now my question is: is the GOCDBClient instructed to get the service type every time, and store it in the cache? I don't see any change for this part.

As a note to Andrei: merging this PR in integration might not be straightforward, especially considering the fact that it uses the Resources handler.

[fstagni]

It should be ok, I would say go on and merge

[atsareg]

The request is badly done because of mixing massive beautification and actual changes - difficult to review and likely to create multiple conflicts