In our commandstatshandler we're asserting that when executing RPCs, we
record the number of spawned commands. To do so we use an RPC that
spawns a Git command. Due to recent changes in our Git command factory
we had to adapt the test though as we are now additionaly spawning a
git-version(1) command to auto-detect the version.

This change is causing flakiness though because we cache the Git
version per binary that is executed: we don't reuse the context, and
when running with bundled Git we now thus randomly use either the old or
the new bundled Git binaries based on a feature flag that uses a random
value. So based on whether this value is the same across both RPC calls
or not we may or may not re-execute git-version(1).

Fix this by reusing the same context for both RPC calls to guarantee
that the feature flag has the same state.