After parsing port ranges conf_ports_spec() checks if we've reached a
chunk delimiter (',') to verify that there isn't extra garbage there.
Rework how we do this to use the recently introduces chunk-end pointer.
This has two advantages:
1) Small, but practical: we don't need to repeat what the valid delimiters
are, that's already handled in the chunk splitting code.
2) Large, if theoretical: this will also given an error if port parsing
overruns a chunk boundary. We don't really expect that to happen, but
it would give very confusing behaviour if it did. strtoul(3), on which
parse_port_range() is based does say it may accept thousands separators
based on locale which means can't entirely be sure it will only accept
strings of digits.
Signed-off-by: David Gibson