Ultra safe dovecot findtime and maxretry settings

Explicitly set the timings and counts for the dovecot jail rather than change the global [DEFAULT] and inherit it for this one jail. These settings are far too safe so a future PR should increase security here.

conf/fail2ban/jail.local

@@ -11,3 +11,5 @@ enabled  = true
 [dovecot]
 enabled = true
 filter  = dovecotimap
+findtime = 30
+maxretry = 20