Avoid double unlock of image load mutex
Avoid double unlock of image load mutex

Causes a runtime crash, with --cache-images:

"fatal error: sync: unlock of unlocked mutex"

kubernetes/minikube,warmchang/minikube,kubernetes/minikube,dlorenc/minikube,dlorenc/minikube,dlorenc/minikube,dlorenc/minikube,kubernetes/minikube,warmchang/minikube,kubernetes/minikube,warmchang/minikube,warmchang/minikube,warmchang/minikube,kubernetes/minikube,kubernetes/minikube,dlorenc/minikube,dlorenc/minikube,warmchang/minikube,dalehamel/minikube,warmchang/minikube,dalehamel/minikube,dlorenc/minikube,kubernetes/minikube,dlorenc/minikube,dalehamel/minikube