Make 'u' go up to the last change listing

Rather than hard code 'u' from a change page to your dashboard, make
it return to the last major listing of changes you were viewing.
This makes it a whole lot easier to navigate through all changes
that you have starred, or have drafts on, or that are in a particular
query result.

Change-Id: I04c5569125633b4e68eb2a93d2bd313a1b632209
Signed-off-by: Shawn O. Pearce <sop@google.com>
8 files changed