Turn off MET significance calculation in CaloMETs for SLHC

[zhenbinwu]

The previous pull request: #4838
might cause potential problems in future. As suggested by Tai Sakuma,
we can just turn off MET significance calculation in CaloMETs.

This pull request reverts the previous changes and turns off MET
significance calculation in RecoMET/METProducers/python/CaloMET_cfi.py.
The MET significance will be set zero in these MET objects.

[cmsbuild]

A new Pull Request was created by @zhenbinwu (Zhenbin Wu) for CMSSW_6_2_X_SLHC.

Turn off MET significance calculation in CaloMETs for SLHC

It involves the following packages:

RecoMET/METAlgorithms
RecoMET/METProducers

@nclopezo, @cmsbuild, @Degano, @StoyanStoynev, @slava77 can you please review it and eventually sign? Thanks.
@nhanvtran, @TaiSakuma, @mmarionncern, @schoef this is something you requested to watch as well.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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@fratnikov, @mark-grimes you are the release manager for this.
You can merge this pull request by typing 'merge' in the first line of your comment.

[mark-grimes]

merge