The functions now read /etc/group and /etc/passwd on host machines.
Android-specific IDs are not recognized in the host.
getpwent and getgrent are still not working though. They require a
bigger refactoring to sequentially advance in the database files.
Bug: 171718702
Test: run assemble_cvd in aosp_cf_arm64_phone
Change-Id: Ie8da382a467bbd0bffac7b4b8592cd871db80181
