docker zuul hangs with inline script

cli.log

 ==> docker: Creating a temporary directory for sharing data... 
 ==> docker: Pulling Docker image: centos:7 
     docker: 7: Pulling from library/centos 
     docker: f1b10cd84249: Already exists 
     docker: c852f6d61e65: Already exists 
     docker: 7322fbe74aa5: Already exists 
     docker: 7322fbe74aa5: Already exists 
     docker: Digest: sha256:bd283727afd9c67d5163ab958238352795233625fa5ca9fef03dfdb2e3c7df4f 
     docker: Status: Image is up to date for centos:7 
 ==> docker: Starting docker container... 
     docker: Run command: docker run -v /var/folders/h_/dd1pr9j52fz0jhyv8lb1ls780000gp/T/packer-docker042755770:/packer-files -d -i -t  centos:7  /bin/bash 
     docker: Container ID: d1e9e2c6f3853d571ec4957b781694f031a78295dbf30040b12bc57cc38b6ba6 
 ==> docker: Uploading files/zuul => /tmp/zuul