fix: restore CmdeployDriver.on_init_relay

1. driver_cmdeploy.py: CmdeployDriver.on_init_relay() was removed
   during the be9d325 refactor but was never moved to the base class as
   the commit message claimed. The method runs scripts/initenv.sh inside
   the builder to create the relay's venv. Without it, every subsequent
   step that calls `source .../venv/bin/activate` fails with
   "No such file or directory".

Author: j4n

src/cmlxc/driver_cmdeploy.py

@@ -90,6 +90,11 @@ def get_test_domain_or_ip(self):
             case _:
                 return self.ct.domain
 
+    def on_init_relay(self, repo_path):
+        """Run scripts/initenv.sh on the builder to create the relay venv."""
+        self.out.print(f"  Running scripts/initenv.sh for {self.ct.shortname} ...")
+        self.bld_ct.bash(f"cd {repo_path} && bash scripts/initenv.sh")
+
     def init_builder(self, source):
         super().init_builder(source)
         if self.filtermail_bin: