Tag Msfcli spec as content

MSP-11147

Tests currently use the real modules directory for test cases, so the
spec should be tagged with :content because it has same performance
issues as other content specs that can potentially load all the modules.

spec/msfcli_spec.rb

@@ -7,7 +7,7 @@ require 'msf/ui'
 require 'msf/base'
 
 
-describe Msfcli do
+describe Msfcli, :content do
   subject(:msfcli) {
     described_class.new(args)
   }