Fix using multiple email addresses for sendmail

busybox sendmail wants space separated list but To: is comma separated
so let sendmail just parse the email body for To:

config/action.d/sendmail-common.conf

@@ -62,7 +62,7 @@ actionunban =
 
 # Your system mail command
 #
-mailcmd = /usr/sbin/sendmail -f "<sender>" "<dest>"
+mailcmd = /usr/sbin/sendmail -f "<sender>" -t
 
 # Recipient mail address
 #

config/jail.conf

@@ -175,6 +175,7 @@ filter = %(__name__)s[mode=%(mode)s]
 
 # Destination email address used solely for the interpolations in
 # jail.{conf,local,d/*} configuration files.
+# comma separated list for multiple addresses
 destemail = root@localhost
 
 # Sender email address used solely for some actions