Cherry-pick: Bump database row version to invalidate ETag cache

When a change is cherry-picked from one branch to another, the following
message is added to the source change:

Patch Set 1: Cherry Picked
This patchset was cherry picked to branch <foo> as commit <bar>

and should be shown when the source change is opened after cherry-pick
action.  While this works as expected on the old change screen, it
doesn't work on new change screen because of ETag caching feature:
change itself isn't changed and NOT_MODIFIED (304) response code is
sent back to client, preventing new rendering.

Remedy this by bumping database row version, like it is already the case
on add/remove reviewers action.

Bug: issue 2710
Change-Id: I0aeaf87fca522a79de0d025384d8b62078e4f0c8
1 file changed