Revert "ifconfig: abort if loading a module fails other than for ENOENT"

This reverts commit 2c24ad3377a6f584e484656db8390e4eb7cfc119.

This change causes some commands to fail, for example when working with
renamed interfaces or when trying to list a nonexistent interface by
name.

PR: 269042
Reported by: dbaio, Michael Paepcke <bugs.fbsd@paepcke.de>
MFC with: 2c24ad3377a6f584e484656db8390e4eb7cfc119