Add ability to block sites in Condor configuration of central manager

[vbrik]

Related to #63

[10:22 AM] 
Gonzalo Merino Hi Vlad. I have a question for you. I see that there is one site in the Grid (actually, accessible via OSG glideins) that appears to fail a lot. My question is how feasible/easy would be for us to configure a “default requirements classad” that we could add automatically to every submitted job in sub-1, that says something like this:

[10:22 AM] 
GLIDEIN_SITE =!= "LIDO_Dortmund"

[10:23 AM] 
kind of keeping a “central black list” ourselves to avoid user jobs to land in specific sites that we detect problemetic

[10:31 AM] 
Vladimir Brik Feasible and probably not hard. NEGOTIATOR_SLOT_CONSTRAINT
might be better than APPEND_REQUIREMENTS, not sure.

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Gonzalo Merino Back to the “bad sites blacklist” topic that we discussed yesterday, sometimes we see problems with OSG sites. The LIDO_Dortmund site that has been failing in the last days for instance is one of those. The Negotiator there is somewhere in glidein2.chtc.wisc.edu or some place else in CHTC. For those, we probably only have the APPEND_REQUIREMENTS option.

----- Today May 4th, 2017 -----
[9:12 AM]
Vladimir Brik Ah, I see. Then yes. APPEND_REQUIREMENTS is the way to go probably.