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.

pkg/fission-cli/cmd/function/test.go

@@ -119,13 +119,13 @@ func (opts *TestSubCommand) do(input cli.Input) error {
 
 	if resp.StatusCode < 400 {
 		fmt.Print(string(body))
-
 		return nil
 	}
 
 	fmt.Printf("Error calling function %s: %d; Please try again or fix the error: %s", m.Name, resp.StatusCode, string(body))
 	err = printPodLogs(input)
 	if err != nil {
+		fmt.Printf("Error getting function logs from pod: %v. Try to get logs from log database", err)
 		return Log(input)
 	}