Replace deprecated readfp method with read_file

The readfp method has been deprecated since version 3.2 [1].

[1] https://docs.python.org/3/library/configparser.html?highlight=deprecated#configparser.ConfigParser.readfp

Change-Id: I2c4c327297b74631d961850e735d5ddc69459e47

os_performance_tools/collectors/mysql.py

@@ -59,7 +59,7 @@ def _get_config():
     try:
         with open(os.path.expanduser("~/.my.cnf")) as dfile:
             parser = configparser.ConfigParser()
-            parser.readfp(dfile)
+            parser.read_file(dfile)
             for k, v in parser.items('client'):
                 args[k] = v
     except IOError as e: