test: skip test-path on Salsa CI

Salsa is the Debian git forge. In the package build environment test-path
always fails as we cannot set up cgroups and so the path unit fails to
start. Skip the test in that environment.

Unfortunately meson doesn't allow to skip individual tests by name.

src/shared/tests.c

@@ -339,6 +339,8 @@ const char *ci_environment(void) {
                 return (ans = "github-actions");
         if (getenv("AUTOPKGTEST_ARTIFACTS") || getenv("AUTOPKGTEST_TMP"))
                 return (ans = "autopkgtest");
+        if (getenv("SALSA_CI_IMAGES"))
+                return (ans = "salsa-ci");
 
         FOREACH_STRING(var, "CI", "CONTINOUS_INTEGRATION") {
                 /* Those vars are booleans according to Semaphore and Travis docs: