When debugging a build (or maintaining an existing packer file), teach `packer build -debug` how to step through individual `boot_command`s in order to triage the packer file.
```
==> vmware-iso: Typing the boot command over VNC...
==> vmware-iso: Pausing after run of step 'boot_command[0]: <enter><wait>'. Press enter to continue.
==> vmware-iso: Pausing after run of step 'boot_command[1]: <enter><wait>'. Press enter to continue.
==> vmware-iso: Pausing after run of step 'boot_command[2]: freebsd-vagrant<enter><wait>'. Press enter to continue.
==> vmware-iso: Pausing after run of step 'boot_command[3]: <down><spacebar>'. Press enter to continue. ^C
```
Change the default behavior from requesting a PTY when executing a
command with the ssh communicator to requesting a PTY only when
configured to do so.
Update the vmware builders to be fully backward compatible with the new
behavior.
This commit fixes errors like this in the vsphere post-processor when using floppy files in the builder step:
Error: File (/var/folders/zl/57c1vmr532z_ryf1scw53_b9ycmxh7/T/packer964492999) could not be found
The configure VMX step re-adds the floppy files, so we need to configure the VMX and _then_ clean the VMX in that order.