Make sure we're not doing a 'negative' timeout

Author: wchen-r7

modules/exploits/multi/http/eventlog_file_upload.rb

@@ -315,6 +315,11 @@ def exploit_java
 
 
   def exploit
+    if datastore['SLEEP'] < 0
+      print_error("The SLEEP datastore option shouldn't be negative")
+      return
+    end
+
     @my_target = pick_target
     if @my_target.nil?
       print_error("#{peer} - Unable to select a target, we must bail.")