(dired-insert-directory): Obey `file-list` and `wildcard`

(dired-insert-directory): Obey `file-list` and `wildcard`

Commit 6f6639d6ed6c's support for wildcards in directories failed
to obey `file-list` and `wildcard` arguments.  Fix it.

* lisp/dired.el (dired-insert-directory): Expand directory wildcards
only if `file-list` is nil and `wildcard` is non-nil.
Also, refer back to `dir-wildcard` instead of recomputing it.
(dired-readin-insert): Pass a non-nil `wildcard` when wildcard
expansion might be needed to preserve former behavior.

(cherry picked from commit f7cf85c3879c6857e8478bef41cce25a94759fb8)