Fix bug when lua script name truncated by dot

Creating a lua diff test with a name containing a dot causes
the name to be parsed incorrectly. Then an attempt is made
to create an tarantool instance with an incorrect name,
resulting in an error. This change fixes the bug.

Fixes #300

lib/tarantool_server.py

@@ -583,7 +583,7 @@ def script(self, val):
                 delattr(self, '_script')
             return
         self._script = os.path.abspath(val)
-        self.name = os.path.basename(self._script).split('.')[0]
+        self.name = os.path.basename(self._script).rsplit(".", maxsplit=1)[0]
 
     @property
     def _admin(self):