zos: return on realloc failure in scandir()
zos: return on realloc failure in scandir()

Fixes: https://github.com/libuv/libuv/issues/2692
PR-URL: https://github.com/libuv/libuv/pull/2693
Reviewed-By: Ben Noordhuis <59bd0a3ff43b32849b319e645d4798d8a5d1e889@bnoordhuis.nl>
Reviewed-By: Richard Lau <8193d74c06330af7778ef55510160e4e561ed6a1@uk.ibm.com>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso