Land rapid7#4697, updates to finder syntax

Updates some Rails 3 style ActiveRecord calls to use the Rails 4 Arel
syntax, in preparation for our move to Rails 4.

Fixes rapid7#4697, also see MSP-12016

Author: mbuck-r7

lib/msf/core/db_manager/vuln.rb

@@ -168,7 +168,7 @@ def report_vuln(opts)
           sname = opts[:proto]
         end
 
-        service = host.services.find_or_create_by_port_and_proto(opts[:port].to_i, proto)
+        service = host.services.where(port: opts[:port].to_i, proto: proto).first_or_create
       end
 
       # Try to find an existing vulnerability with the same service & references

lib/msf/core/db_manager/workspace.rb

@@ -4,7 +4,7 @@ module Msf::DBManager::Workspace
   #
   def add_workspace(name)
   ::ActiveRecord::Base.connection_pool.with_connection {
-    ::Mdm::Workspace.find_or_create_by_name(name)
+    ::Mdm::Workspace.where(name: name).first_or_create
   }
   end