Improve error messages.

-Include arguments for initgroups(3), setgroups(2), setres{g,u}id(2).
-Add "failed" for setns(2), unshare(2), initgroups(3), setgroups(2),
and setres{g,u}id(2), mount(2), and various prctl(2)'s.
-Use actual flag names for unshare(2) errors. Makes googling/referring
to man pages easier.

And two nits:
-"net_bring_up_loopback" -> "config_net_loopback", shorter, clearer.
-Fix one long line.

Bug: 33264665
Test: Builds on Android and Linux.

Change-Id: Id1bc42186f9d7f0724ff9897f364656f52202e44
1 file changed