Set a mode when calling open with O_CREAT

[andrew]

Summary

We shouldn't be creating files without also setting the mode, otherwise
the kernel will use whatever value is in the third argument location.

[brooks]

LGTM. I'd commit the netbsd ones separately and forward the commit some appropriate netbsd list (probably tech-kern).

[ngie]

@brooks: LGTM. I'd commit the netbsd ones separately and forward the commit some appropriate netbsd list (probably tech-kern).

I can handle creating the PRs on their end for this. Just need to create a NetBSD VM, checkout the sources, etc :) (since I deleted it a while ago).