You are asking two different questions here, one about kube-apiserver configuration, one about troubleshooting your StorageClass.
Here’s an answer for your first question:
kube-apiserver is running as a Docker container on your master node. Therefore, the binary is within the container, not on your host system. It is started by the master’s kubelet from a file located at /etc/kubernetes/manifests. kubelet is watching this directory and will start any Pod defined here as “static pods”.
To configure kube-apiserver command line arguments you need to modify /etc/kubernetes/manifests/kube-apiserver.yaml on your master.