Make location of caCert, tokenFile and namespaceFile configurable in Webhook Proxy

[ungerts]

Locations of caCert, tokenFile and namespaceFile are currently hard coded in main.go. Making these locations configurable would allow for easier setup of local dev environments.

Proposal is:

namespaceFileDefault  = "/var/run/secrets/kubernetes.io/serviceaccount/namespace"
namespaceFileEnvVar   = "NAMESPACE_FILE"
tokenFileDefault      = "/var/run/secrets/kubernetes.io/serviceaccount/token"
tokenFileEnvVar       = "TOKEN_FILE"
caCertDefault         = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
caCertEnvVar          = "CA_CERT_FILE"

[ungerts]

Also server port is now configurable

[michaelsauter]

@ungerts This has not been merged yet, right?