Remove the account error scrollbook from the blist as notifications have replaced it.
Also clear account errors when we attempt a new connection which made clearing
the errors after the account has connected redundant.
Testing Done:
Caused the same account to get disconnected between pidgin 2 and 3 to verify notifications were working as expected.
Bugs closed: PIDGIN-17640
Reviewed at https://reviews.imfreedom.org/r/1521/