Do not translate log messages.

[fupingxie]

We should use "msg = _('My message.')" instead "msg = _(variable_containing_msg)" when logging message.

For example: do not do this:
# WRONG
msg = _(variable_containing_msg)
w_msg = _LW(variable_warning_msg)

Instead, use this style:

# RIGHT
msg = _('My message.')
w_msg = _LW('My warning message')

refer to：
https://docs.openstack.org/oslo.i18n/latest/user/guidelines.html#using-a-marker-function

[OpenStack Infra (hudson-openstack)]

Change abandoned by fupingxie (<email address hidden>) on branch: master
Review: https://review.openstack.org/603962