The key for the Store cache was not adjusting properly for account
changes (such as port changes, etc...). As such, it was possible to
get an invalid store.
Now, there's problem with leaking Account objects if the store account
changes (see bug 4440839). This is "okay" for now since account changes
are fairly uncommon and Account objects are light. However, this should
be fixed at some point.
Change-Id: I4ddcbc3e2759b7b1374d0300706373678dedec94
581e3c2333