avoid using curl when downloading ocm

lib/launchers/o_c_m_cluster.rb

@@ -168,13 +168,11 @@ def download_ocm_cli
           raise "Unsupported OS"
         end
       end
-      #doesn't work
-      #File.open('/tmp/ocm', 'wb') do |file|
-      #  @result = Http.get(url: url) do |chunk|
-      #    file.write chunk
-      #  end
-      #end
-      shell("curl -L #{url} -o /tmp/ocm")
+      File.open('/tmp/ocm', 'wb') do |file|
+        @result = Http.get(url: url, raise_on_error: true) do |chunk|
+          file.write chunk
+        end
+      end
       File.chmod(0775, '/tmp/ocm')
       return '/tmp/ocm'
     end