Fix fn test failed to query logs from log database (#1401)

When `fn test` failed to retrieve logs from the function
pod, it turns to query logs from the log database. However,
the logdb type flag is not set to `fn test`, hence the logdb
type is empty (even without default value) and cause `fn logs`
returns an error due to unable to find the corresponding log
database type.

This PR adds logdb type flag to `fn test` to resolve the problem.

test/tests/test_ingress.sh

@@ -75,9 +75,11 @@ createFn() {
 
     log "Creating function"
     fission fn create --name $functionName --env $env --code $ROOT/examples/nodejs/hello.js
+    sleep 3
 
     log "Doing an HTTP GET on the function's route"
     response=$(fission fn test --name $functionName)
+    echo $response
 
     log "Checking for valid response"
     echo $response | grep -i hello