Settings: Fix settings force close when adding a account.

ChooseAccountActivity is started as activity in executePendingTransactions(),
SettingsPreferenceFragment finish() will call executePendingTransactions() again,
then FragmentManager will throw "Recursive entry" IllegalStateException.

Use Activity finish() directly.

Change-Id: Iae32b6bb61a8091c5265bc887f92307cf05d4092
CRs-Fixed: 1031518