FIX: workaround lock rotation regression on "b2g-18.0.2013-05-22"

gaia system app nodePrincipal.appStatus reported as "app not installed"
(nodePrincipal.appStatus == APP_STATUS_NOT_INSTALLED)

if origin is "app://system.gaiamobile.org" in mozLockOrientation method, it doesn't deny rotation lock even if its appStatus is reported as not installed.

Console Messages:
```
Error: deny mozLockOrientation:
Source File: jar:file:///.../b2g-prosthesis@mozilla.org.xpi!/components/SimulatorScreen.js
Line: 210
```