msfenv compatibility with Pro

MSP-9653

lib/msfenv.rb should only load the framework environment to initialize
Metasploit::Framework::Application if a Rails.application is not
defined, otherwise it will clash with the Rails application in prosvc.

lib/msfenv.rb

@@ -10,4 +10,10 @@
 root = Pathname.new(__FILE__).expand_path.parent.parent
 config = root.join('config')
 require config.join('boot')
-require config.join('environment')
+
+# Requiring environment will define the Metasploit::Framework::Application as the one and only Rails::Application in
+# this process and cause an error if a Rails.application is already defined, such as when loading msfenv through
+# msfconsole in Metasploit Pro.
+unless defined?(Rails) && !Rails.application.nil?
+  require config.join('environment')
+end