Jann - Ove Risvik authored Jul 08, 2016 and Natanael Copa committed Aug 11, 2016

fixes #4802

Seems like iscsiadm relies on checking optopt for checking if there's an
error, instead of checking whether opterr is set or if getopt returns
'?' and then using optopt to retrieve the option that it didn't
recognize.

For some reason musl sets optopt to the last option parsed even if it
was valid. Is musl supposed to do that? glibc doesn't behave this way.
The posix standard for getopt also reads like optopt is only supposed to
be set when there's an error.