Revert "monitor: delegate argument checking to argparse"

This reverts commit 4a992aaa.

runpromise takes arguments from command line, but also read some from
a config file, so indeed it is mandatory to know partition_folder's
value, but it is not mandatory to pass it as an argument from the
command line

slapos/monitor/runpromise.py

@@ -28,7 +28,7 @@ def getArgumentParser():
   parser = argparse.ArgumentParser()
   parser.add_argument('-c', '--config', dest='config_file',
                       help='The Path of configuration file to load.')
-  parser.add_argument('-p', '--partition-folder', required=True,
+  parser.add_argument('-p', '--partition-folder',
                       help='Base path of the partition.')
   parser.add_argument('-L', '--log-folder',
                       help='Folder where promises will write logs.')
@@ -124,6 +124,9 @@ class MonitorPromiseLauncher(object):
       with open(self.config.pid_path, 'w') as fpid:
         fpid.write(str(os.getpid()))
 
+    if not self.config.partition_folder:
+      raise ValueError("Partition folder is not specified")
+
     parameter_dict = {
       'promise-timeout': self.config.promise_timeout or promise_timeout,
       'promise-folder': os.path.join(self.config.partition_folder, 'etc', 'plugin'),