[Android] Fix the incorrect context usage for HttpAuthDataBase.

The database file should be in the app's data directory. However,
if using the context of runtime lib package, Android doesn't allow
to create it. Fix it by using the application context which is for
the runtime client side.

BUG=#1002
Merge pull request #1005 from yongsheng/1002

[Android] Fix the incorrect context usage for HttpAuthDataBase.