[tempauth] update token if its value changes or expires

In current codes, tempauth token will be updated only when it expires. In
token's lifetime, any changes in tempauth config file doesn't update token,
which means if you update your config file and restart proxy server, the
role in runtime might not change. So a good fix is updating token when
it changes or expires.

fixes bug #1201678

Change-Id: Ieb080e87268e16d0a2e5896431aa41fcedc7a900
Merge "[tempauth] update token if its value changes or expires"