Bug 1076040 - Ensure watched repo navbar appears on initial page load

This fixes Bugzilla bug [1076040](https://bugzilla.mozilla.org/show_bug.cgi?id=1076040).

In it we ensure we set `locationPath` only after `locationChangeSuccess` has occurred. Otherwise its value on initial page load can be null, instead of `/jobs`. Which it needs to be, for a successful ng-show in its particular partial.

Here's the before and after the fix, on initial load:

![initialloadcurrent](https://cloud.githubusercontent.com/assets/3660661/4532258/4335d574-4d91-11e4-89fc-bdc991815e2b.jpg)

![initialloadfixed](https://cloud.githubusercontent.com/assets/3660661/4532259/46ca8450-4d91-11e4-990d-5f4d782eb868.jpg)

The display state of the jobs menu was also impacted.

Chrome didn't show the same problem in dev/stage/prod, but it did show the problem in a local server. Firefox appeared to show the problem in all.

A note, the initial work which orphaned that value appear to be about a month ago, in case there's investigation or more context needed. It is https://github.com/mozilla/treeherder-ui/commit/b413f839545ac12368187fba680dd9c447973429#diff-4168352fd16d2e6758c883cc406005abL206

Everything seems to appear correctly on both browsers I've tested with a local server.

Tested on Windows:
FF Release **32.0.3**
Chrome Latest Release **37.0.2062.124 m**

Adding @wlach and @camd for review.