Move split_command to utils

This patch moves _split_command from IronicPythoAgent class to
utils module. Also fixes import looping.

Change-Id: Ibf2b0b3885286b9ad78db64cf9e195de4ad627ad

ironic_python_agent/utils.py

@@ -40,3 +40,14 @@ def execute(*cmd, **kwargs):
     LOG.debug(gtu._('Command stdout is: "%s"') % result[0])
     LOG.debug(gtu._('Command stderr is: "%s"') % result[1])
     return result
+
+
+def split_command(command_name):
+    command_parts = command_name.split('.', 1)
+    if len(command_parts) != 2:
+        #NOTE(agordeev): fix to avoid import looping
+        from ironic_python_agent import errors
+        raise errors.InvalidCommandError(
+            'Command name must be of the form <extension>.<name>')
+
+    return (command_parts[0], command_parts[1])