Strip excess slashes when joining path parts in files.sync operation.

We have to manually join the parts because `path.join` depends on the
OS of the place pyinfra is executing, not the target host.

Author: Fizzadar

pyinfra/operations/files.py

@@ -484,7 +484,8 @@ def sync(
                 # Join remote as unix like
                 '/'.join(
                     item for item in
-                    (dest, remote_dirpath, filename)
+                    # Remove any existing / where we're going to join
+                    (dest.rstrip('/'), remote_dirpath.strip('/'), filename.lstrip('/'))
                     if item
                 ),
             ))