KVM: starting network minikube-net: Network is already in use by interface

[medyagh]

 Not passing HTTP_PROXY=localhost:38041 to docker env.
	* Failed to start kvm2 VM. "minikube start -p functional-20200821114009-297274" may fix it: creating host: create: Error creating machine: Error in driver during machine creation: ensuring active networks: starting network minikube-net: virError(Code=1, Domain=0, Message='internal error: Network is already in use by interface br-487e1305fa05')

a seen in integration flakes
https://storage.googleapis.com/minikube-builds/logs/9045/007ad31/KVM_Linux.html#fail_TestFunctional%2fserial%2fStartWithProxy

[medyagh]

CC: @josedonizetti

[tstromberg]

Hmmm -- are we trying to share a single minikube network name across clusters? It seems odd that the network name is minikube-net but the VM name is functional-20200821114009-297274.

[josedonizetti]

@medyagh @tstromberg The kvm driver does share the same network for all vms. To change it we need some kind of IPAM, because right now the subnet used on the network is fixed: https://github.com/kubernetes/minikube/blob/master/pkg/drivers/kvm/network.go#L41

We need a different subnet per VM.

[priyawadhwa]

Closing in favor of #9610