Fix relative host path resolution for volume bind mount source

e03d675b9b broke relative host path
resolution by deleting os.chdir(). After this commit current working
directory is not relevant anymore.

Fixes e03d675b9b.

Signed-off-by: Monika Kairaityte <monika@kibit.lt>

podman_compose.py

@@ -421,6 +421,7 @@ async def assert_volume(compose: PodmanCompose, mount_dict: dict[str, Any]) -> N
                 os.makedirs(mount_src, exist_ok=True)
             except OSError:
                 pass
+        mount_dict["source"] = mount_src
         return
     if mount_dict["type"] != "volume" or not vol or not vol.get("name"):
         return