Add a env var to use in-memory obj server in func

Add an environment variable to enable the use of the in-memory object
server during in-process functional test runs.

It might be worth-while to just run under both object servers in-tree,
but this at least enables it, without having to figure out how to make
two test runs in two different environments.

DocImpact

Change-Id: Id76b008e1f273c639ae61550affddc32c5d7c419
Signed-off-by: Thiago da Silva <thiago@redhat.com>
Merge "Add a env var to use in-memory obj server in func"