test: Fix start_external_auth_daemon to work with git 2.34.1
test: Fix start_external_auth_daemon to work with git 2.34.1

When running the test suite as root and the lxd source code directory was owned by non-root
we were getting the following error:

go build ./...
error obtaining VCS status: exit status 128
	Use -buildvcs=false to disable VCS stamping.

This is due to root's git config not trusting the lxd source directory.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

lxc/lxd,hallyn/lxd,hallyn/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd