chore(http-client): small refactor and use fstrings

rhodecode/lib/vcs/client_http.py

@@ -148,7 +148,7 b' def _streaming_remote_call(url, payload,'
 
 class ServiceConnection(object):
     def __init__(self, server_and_port, backend_endpoint, session_factory):
-        self.url = urllib.parse.urljoin('http://%s' % server_and_port, backend_endpoint)
+        self.url = urllib.parse.urljoin(f'http://{server_and_port}', backend_endpoint)
         self._session_factory = session_factory
 
     def __getattr__(self, name):
@@ -170,8 +170,8 b' class ServiceConnection(object):'
 class RemoteVCSMaker(object):
 
     def __init__(self, server_and_port, backend_endpoint, backend_type, session_factory):
-        self.url = urllib.parse.urljoin('http://%s' % server_and_port, backend_endpoint)
-        self.stream_url = urllib.parse.urljoin('http://%s' % server_and_port, backend_endpoint+'/stream')
+        self.url = urllib.parse.urljoin(f'http://{server_and_port}', backend_endpoint)
+        self.stream_url = urllib.parse.urljoin(f'http://{server_and_port}', backend_endpoint+'/stream')
 
         self._session_factory = session_factory
         self.backend_type = backend_type