Moved the 'add_delay_jitter' function to scanner.rb so that all modules can benefit from it if needed

lib/msf/core/auxiliary/scanner.rb

@@ -299,6 +299,36 @@ def scanner_show_progress
   end
 end
 
+def add_delay_jitter(_delay, _jitter)
+  # Introduce the delay
+  delay_value = _delay.to_i
+  original_value = delay_value
+  jitter_value = _jitter.to_i
+  
+  # Retrieve the jitter value and delay value 
+  # Delay = number of milliseconds to wait between each request
+  # Jitter = percentage modifier. For example:
+  # Delay is 1000ms (i.e. 1 second), Jitter is 50.
+  # 50/100 = 0.5; 0.5*1000 = 500. Therefore, the per-request
+  # delay will be 1000 +/- a maximum of 500ms. 
+  if delay_value>0
+    if jitter_value>0
+       rnd = Random.new
+       if (rnd.rand(2)==0)
+          delay_value += rnd.rand(jitter_value)
+       else
+          delay_value -= rnd.rand(jitter_value)
+       end 
+       if delay_value<0
+          delay_value = 0 
+       end 
+    end 
+    final_delay = delay_value.to_f/1000.0
+    vprint_status("Delaying for #{final_delay} second(s) (#{original_value}ms +/- #{jitter_value}ms)")
+    sleep final_delay
+  end 
+end
+
 end
 end