switch to using a credential helper rather than a credential store

Author: lerouxb

.evergreen/docker-config/bin/docker-credential-from-env

@@ -2,7 +2,11 @@
 
 set -euo pipefail
 
-DOCKER_HUB_URL="https://index.docker.io/v1/"
+# index
+#DOCKER_HUB_URL="https://index.docker.io/v1/"
+
+# registry (maybe?)
+DOCKER_HUB_URL="registry.hub.docker.com"
 
 STDIN=$(cat)
 

.evergreen/docker-config/config.json

@@ -1,6 +1,5 @@
 {
-	"auths": {
-		"https://index.docker.io/v1/": {}
-	},
-	"credsStore": "from-env"
-} 
+  "credHelpers": {
+    "registry.hub.docker.com": "from-env"
+  }
+}