Export API host from parent process to child process. (#115)

diff --git a/openwhisk/actionProxy.go b/openwhisk/actionProxy.go
index e922e66..d9e7068 100644
--- a/openwhisk/actionProxy.go
+++ b/openwhisk/actionProxy.go
@@ -71,6 +71,7 @@
 
 //SetEnv sets the environment
 func (ap *ActionProxy) SetEnv(env map[string]interface{}) {
+	ap.env["__OW_API_HOST"] = os.Getenv("__OW_API_HOST")
 	for k, v := range env {
 		s, ok := v.(string)
 		if ok {