B #6299: Increase delay before ipset destroy

This will give kernel some more time to clean up before attemting to
destroy the associated ipsets. Otherwise it may fail with: "Set cannot be
destroyed: it is in use by a kernel component"

src/vnm_mad/remotes/lib/security_groups_iptables.rb

@@ -616,7 +616,7 @@ module SGIPTables
         remove_chains_6.each {|c| commands.add :ip6tables, "-X #{c}" }
 
         # delay to allow kernel to clean up
-        commands.add 'sleep', '0.1'
+        commands.add 'sleep', '0.5'
 
         ipset_list.lines.each do |line|
             if line.match(/^#{chain}(-|$)/)