• [x ] I have tried with the latest version of my channel (Stable or Edge)
• I have submitted Diagnostics
• I have included the Diagnostics ID in this Issue
• macOS Version: 10.12.6

Expected behavior

should not override existing /usr/local/bin/kubectl installation

Actual behavior

/usr/local/bin/kubectl is replaced with docker's installation. The existing one is renamed to kubectl.backup.

Steps to reproduce the behavior

1. brew install kubectl

$ ls -l /usr/local/bin/kubectl /usr/local/bin/kubectl -> ../Cellar/kubernetes-cli/1.10.1/bin/kubectl

2. Install docker-for-mac edge, enable kuberneters

$ ls -l /usr/local/bin/kubectl /usr/local/bin/kubectl -> /Applications/Docker.app/Contents/Resources/bin /usr/local/bin/kubectl.backup -> ../Cellar/kubernetes-cli/1.10.1/bin/kubectl

The version installed by Docker-for-Mac is v1.9.x, it doesn't work with some features that requires v1.10.x, such as AWS authentication with heptio-aws-auth plugin.

Maybe Docker-for-Mac installer should test existing /usr/local/bin/kubectl and not try to replace it, or at least gives users an option to override or not?