ENH: actionunban back to a sed command

per https://github.com/fail2ban/fail2ban/pull/182#discussion_r3999128

config/action.d/hostsdeny.conf

@@ -40,11 +40,7 @@ actionban = IP=<ip> &&
 # Tags:    See jail.conf(5) man page
 # Values:  CMD
 #
-# Original:
-#actionunban = IP=<ip> && sed -i.old /ALL:\ $IP/d <file>
-
-# -i is not supported under Solaris 10/OpenSolaris
-actionunban = IP=<ip> && perl -ne "print unless (/^ALL:\s$IP/)" -i <file>
+actionunban = IP=<ip> && sed  /ALL:\ $IP/d <file> > <file>.new && mv <file>.new <file>
 
 [Init]