remove 'virt cluster pmtpa' from ganglia

the only member of this is virt0 which we are going
to shut down and these show up in logs on nickel:

nickel /usr/sbin/gmetad[12043]:
data_thread() got no answer from any [Virtualization cluster pmtpa] datasource

nickel /usr/sbin/gmetad[12043]:
data_thread() for [Virtualization cluster pmtpa] failed to contact node 208.80.152.32

so i suppose we can as well remove it

Change-Id: Ibdee8990050ac5a7e0a193dc34cfadc6283d63c3
Merge "remove 'virt cluster pmtpa' from ganglia" into production