Modified the docker builder's default run_command to specify the shell via the entrypoint command line argument as suggested by @vrubiolo in #6920.
Modified the docker builder's default run_command to specify the shell via the entrypoint command line argument as suggested by @vrubiolo in #6920.

rnaveiras/packer,bryson/packer,tas50/packer,timsutton/packer,grubernaut/packer,rnaveiras/packer,paulmey/packer,mkuzmin/packer,dave2/packer,hashicorp/packer,dave2/packer,grubernaut/packer,ricardclau/packer,youhong316/packer,tas50/packer,youhong316/packer,mkuzmin/packer,mkuzmin/packer,hashicorp/packer,grubernaut/packer,pecigonzalo/packer,grubernaut/packer,mitchellh/packer,dave2/packer,youhong316/packer,ricardclau/packer,mitchellh/packer,grubernaut/packer,paulmey/packer,dave2/packer,rnaveiras/packer,tas50/packer,rnaveiras/packer,timsutton/packer,timsutton/packer,pecigonzalo/packer,ricardclau/packer,rnaveiras/packer,bryson/packer,rnaveiras/packer,bryson/packer,mitchellh/packer,bryson/packer,ricardclau/packer,paulmey/packer,mitchellh/packer,paulmey/packer,hashicorp/packer,mkuzmin/packer,hashicorp/packer,dave2/packer,tas50/packer,paulmey/packer,paulmey/packer,timsutton/packer,pecigonzalo/packer,bryson/packer,tas50/packer,bryson/packer,grubernaut/packer,timsutton/packer,mkuzmin/packer,youhong316/packer,youhong316/packer,mitchellh/packer,dave2/packer,mkuzmin/packer,timsutton/packer,youhong316/packer,tas50/packer,ricardclau/packer,ricardclau/packer,pecigonzalo/packer