Fix #4163 - Update merge_check_key to keep up with 2.1.4 change

The merge_check_key method (found in Msf::Module::ModuleInfo)) uses
respond_to? to check is our object includes a merge_info_description
method before merging descriptions. The respond_to? method in 2.1.4
by default no longer checks private and protected methods, and this
is breaking our merge_check_key method.

Fix #4163

lib/msf/core/module/module_info.rb

@@ -74,7 +74,7 @@ module Msf::Module::ModuleInfo
   # Checks and merges the supplied key/value pair in the supplied hash.
   #
   def merge_check_key(info, name, val)
-    if (self.respond_to?("merge_info_#{name.downcase}"))
+    if (self.respond_to?("merge_info_#{name.downcase}", true))
       eval("merge_info_#{name.downcase}(info, val)")
     else
       # If the info hash already has an entry for this name