LIB-51: darwin: don't close the fd after toc read
LIB-51: darwin: don't close the fd after toc read

This obviously broke all later disc reads,
including MCN and ISRCs.
This was introduced in fe2d1fb955,
but not at all easy to see in the diff.

phw/libdiscid,metabrainz/libdiscid,phw/libdiscid,metabrainz/libdiscid