o Fixed multiple NSE scripts that weren't always properly closing their

sockets.  The error message was:
    "bad argument #1 to 'close' (nsock expected, got no value)"

scripts/SMTPcommands.nse

@@ -48,7 +48,7 @@ action = function(host, port)
         result1 = try(socket:receive_lines(1))
 
         if not string.match(result1, "^250") then
-                socket.close()
+                socket:close()
 -- TODO: use print_debug instead
                 return "EHLO with errors or timeout.  Enable --script-trace to see what is happening."
         end
@@ -70,7 +70,7 @@ action = function(host, port)
 	result2 = try(socket:receive_lines(1))
 
 	if not string.match(result2, "^214") then
-		socket.close()
+		socket:close()
 -- TODO: use print_debug instead
 		return "HELP with errors or timeout.  Enable --script-trace to see what is happening."
 	end

scripts/SQLInject.nse

@@ -41,7 +41,7 @@ local maxdepth = 10
 local get_page_from_host
 
 local soc
-local catch = function() soc.close() end
+local catch = function() soc:close() end
 local try = nmap.new_try(catch)
 
 portrule = shortport.service("http")

scripts/bruteTelnet.nse

@@ -9,7 +9,7 @@ require('stdnse')
 require('strbuf')
 
 local soc
-local catch = function() soc.close() end
+local catch = function() soc:close() end
 local try = nmap.new_try(catch)
 
 portrule = shortport.port_or_service(23, 'telnet')

scripts/robots.nse

@@ -34,7 +34,7 @@ end
 action = function(host, port)
 	local soc, lines, status
 
-	local catch = function() soc.close() end
+	local catch = function() soc:close() end
 	local try = nmap.new_try(catch)
 
 	-- connect to webserver 

scripts/zoneTrans.nse

@@ -263,7 +263,7 @@ end
 
 action = function(host, port)
 	local soc, status, data
-	local catch = function() soc.close() end
+	local catch = function() soc:close() end
 	local try = nmap.new_try(catch)
 	
 	-- can't do anything without a hostname