feat(minishift): Respect vm-driver on multiple levels

The vm-driver to choose will be detected by (in this order):

* from the env var VM_DRIVER
* from the minishift vm-driver config in the *minishift* profile
* "hyperkit" on macOs

If none is found, then minishift is started without vm-driver option
(which falls back to minishift defaults)

Author: rhuss

etc/scripts/install-on-minishift.sh

@@ -15,15 +15,23 @@ OPENSHIFT_VERSION=${OPENSHIFT_VERSION:-v3.11.0}
 MEMORY=${MEMORY:-10GB}
 CPUS=${CPUS:-4}
 DISK_SIZE=${DISK_SIZE:-50g}
-VM_DRIVER=${VM_DRIVER:-}
 
-# Set hyperkit as default on macOs
-if [[ -z "${OSTYPE}" && $(uname) == "Darwin" ]] || [ "${OSTYPE#darwin}" != "${OSTYPE}" ]; then
-  VM_DRIVER=${VM_DRIVER:-hyperkit}
+if [ -z "${VM_DRIVER}" ]; then
+  # check for default driver
+  VM_DRIVER=$(minishift config get vm-driver --profile minishift)
+  if [ -z "$VM_DRIVER" ] || [ $VM_DRIVER = "<nil>" ]; then
+    if [[ -z "${OSTYPE}" && $(uname) == "Darwin" ]] || [ "${OSTYPE#darwin}" != "${OSTYPE}" ]; then
+      # set hyperkit as default on macOs
+      VM_DRIVER="hyperkit"
+    else
+      # no driver to set
+      VM_DRIVER=""
+    fi
+  fi
 fi
 
 # blow away everything in the knative profile
-minishift profile delete knative --force
+minishift profile delete knative --force >/dev/null 2>&1
 
 # configure knative profile
 minishift profile set knative