In order for projects to use the namespace property of Targets
in a backwards compatible way (To support rolling upgrades),
a Target may now belong to more than a single namespace (i.e.
'namespace1' and None). This way, if the server is upgraded first,
the version that introduces namespaces to a project will place
the server RPC methods in ['some_namespace', None]. Pre-upgrade
agents will send messages in the null namespace while post-upgrade
agents will send messages in 'some_namespace', and both will be
accepted.
Change-Id: I713fe9228111c36aa3f7fb95cbd59c99100e8c96
Closes-Bug: #1430984