Override requests for DB_SLAVE when submitting new content

Multiple spots are having related issues about not finding
the posts they are supposed to.  AFAICT most of this is happening
because TreeRepository is trying to read from the SLAVE when the
data has not yet been commited to MASTER.

This fix will result in TreeRepository getting back the master
connection even though its requesting a slave when the request
is submitting new content.

Unsure how to test directly, the error is only occuring on beta labs.
After merging verify that new submissions are working properly
on beta.

Bug: 68531
Bug: 69712
Change-Id: Ie39948d339f028ebac925c96a5186ba9aaf16b06
Merge "Override requests for DB_SLAVE when submitting new content"