There is currently only one metadata-agent per network node,
which could be handling connections from hundreds or thousands
of metadata-namespace-proxy processes.
This change addes a new "metadata_workers = XX" to the ini file
to support creating more workers to help improve performance.
Change-Id: Ib9ebcfc543a83982dd93db79c7dc631283fd3bfa
Partial-bug: #1274536