install script from omnitruck fails when dpkg/yum/etc is temporarily locked

Version:

current at https://omnitruck.chef.io/install.sh

Environment:

I am running the script on Ubuntu 18.04 but the problem being described here is OS-agnostic and applies to all installation methods that use a package manager that uses a lock so that two package processes cannot run at once.

Scenario:

I am attempting to install chef using the install.sh script, coincidentally at the same time as another process is using dpkg (or another package manager).

Steps to Reproduce:

1. launch a long/slow dpkg or yum process
2. in another shell, run install.sh

Expected Result:

install script waits for dpkg/yum to become unlocked

Actual Result:

   Installing chef 
   installing with dpkg...
   dpkg: error: dpkg frontend is locked by another process
   Installation failed
   Version: 

Start with the current install.sh at https://omnitruck.chef.io/install.sh and trace how it invokes dpkg, yum, and other package managers. Reproduce the failure by running the script while a package-manager process holds its lock. Done means the installation waits for the lock to clear instead of immediately reporting an installation failure.