Skip a vc-bzr test if run as root

* test/lisp/vc/vc-bzr-tests.el (vc-bzr-test-faulty-bzr-autoloads):
Skip this test when run as root.  This works around a race
condition in root-specific code in vc-mode-line when deleting a file.

; Do not merge to master, instead fix vc-mode-line there.
1 job for emacs-26 in 2 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #336
test

00:00:02

 
Name Stage Failure
failed
test Test There has been a runner system failure, please try again
Running with gitlab-runner 11.4.2 (cf91d5e1)
on gitlab-runner-docker cff9d373
Using Docker executor with image debian:stretch ...
Pulling docker image debian:stretch ...
Using docker image sha256:4879790bd60d439cfe39c063660eef7af525d5f6f1cbb701a14c7cfc11cbfcf7 for debian:stretch ...
ERROR: Job failed (system failure): Error response from daemon: open /var/run/docker/libcontainerd/containerd/45b7f2e9db8ecc7a444a9f8174e45c5a3961b0b14f7eae6f109ab348744aa329/init/shim-log.json: no such file or directory (executor_docker.go:1015:0s)