accounts: don't remove accounts while device is in safe mode

Userspace apps are not available in safe mode, so authenticators are not available when
the system starts and checks all accounts. Just ignore these accounts and not add them
to the list of accounts.

JIRA: CYAN-4074
Issue: https://jira.cyanogenmod.org/browse/CYAN-4074
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Change-Id: I9cac5084c29fe33a0215ab4a9e693f58712438ac