Bug 1491390 - When searching for baseline coverage tests, only look at the test name. r=jmaher

This patch fixes an issue where a suite was being found in the full path to the test which led to the baseline coverage tests being considered on a per-suite basis (like browser-chrome), when it should be on a per-file-extension basis for '.html' files. This is fixed by only considering the test name and excluding the full path to it.

Differential Revision: https://phabricator.services.mozilla.com/D5890

--HG--
extra : moz-landing-system : lando

testing/mozharness/mozharness/mozilla/testing/codecoverage.py

@@ -419,7 +419,7 @@ class CodeCoverageMixin(SingleTestMixin):
                     with open(grcov_file, 'r') as f:
                         data = json.load(f)
 
-                    if suite in test:
+                    if suite in os.path.split(test)[-1]:
                         baseline_tests_suite_cov[suite] = data
                     else:
                         _, baseline_filetype = os.path.splitext(test)