Possible fix for CI_SERVER issue in VLS CI

Code using `CI_SERVER` was added recently to track something.  It
attempts to short-cut if `CI_SERVER` is not set, but on gitlab it
is set to `yes`.  https://docs.gitlab.com/ee/ci/variables/

Instead use `CI_SERVER_URL`, maybe that is what is intended?

.github/workflows/ci.yaml

@@ -15,7 +15,7 @@ env:
   # of a bit of compile time.
   RUST_PROFILE: release
   SLOW_MACHINE: 1
-  CI_SERVER: "http://35.239.136.52:3170"
+  CI_SERVER_URL: "http://35.239.136.52:3170"
 
 jobs:
   prebuild:

conftest.py

@@ -6,7 +6,7 @@
 from time import time
 import unittest
 
-server = os.environ.get("CI_SERVER", None)
+server = os.environ.get("CI_SERVER_URL", None)
 
 github_sha = (
     subprocess.check_output(["git", "rev-parse", "HEAD"]).decode("ASCII").strip()