fixed issues with deleting files and issue with json method not defined for the mock-double for rspec-tests in lib

spec/lib/docker_client_spec.rb

@@ -7,7 +7,7 @@ describe DockerClient, docker: true do
   let(:execution_environment) { FactoryGirl.build(:ruby) }
   let(:image) { double }
   let(:submission) { FactoryGirl.create(:submission) }
-  let(:workspace_path) { '/tmp' }
+  let(:workspace_path) { '/tmp/codeocean_dockertest' }
 
   describe '.check_availability!' do
     context 'when a socket error occurs' do