#160 sysAppLaunchCmdSystemLock issue

[Alexander R. Pruss]

The KeyRing code is supposed to clear the password from memory on system lock. However, it does this by checking for the sysAppLaunchCmdSystemLock launch code. But this launch code is sent only to the Security app.

One workaround is to clear the password from memory whenever the device is turned on in locked mode (use PrefGetPreference(prefDeviceLocked) and register for one or both wakeup notifications).