Add interfaces name prefixes for KVM bridges

[nvazquez]

Add a note to consider for interfaces names when configuring bridges for KVM networking. Otherwise, the agent will fail to be configured with error:

2021-05-13 18:53:08,587 DEBUG [kvm.resource.LibvirtComputingResource] (agentRequest-Handler-5:null) (logid:4b3902b9) matchPifFileInDirectory: file name 'cdbr_bond1'
2021-05-13 18:53:08,587 DEBUG [kvm.resource.LibvirtComputingResource] (agentRequest-Handler-5:null) (logid:4b3902b9) failing to get physical interface from bridge cloudbr1, did not find an eth*, bond*, team*, vlan*, em*, p*p*, ens*, eno*, enp*, or enx* in /sys/devices/virtual/net/cloudbr1/brif

[andrijapanicsb]

@blueorangutan docbuild

[blueorangutan]

@andrijapanicsb a Jenkins job has been kicked to build the document. I'll keep you posted as I make progress.

[blueorangutan]

Doc build preview: http://qa.cloudstack.cloud/docs/WIP-PROOFING/pr/214. (SL-JID 60)

[andrijapanicsb]

LGMT