fixed the way of iterating over the range of map.

Fixed the following errors:
1. Request(0) causes a dead loop when the map is full and map.last == BEGIN.
2. When map.last is the only available port (or ip), Request(0) returns ErrAllPortsAllocated (or ErrNoAvailableIPs). Exception is when map.last == BEGIN.

Signed-off-by: shuai-z <zs.broccoli@gmail.com>
Merge pull request #8699 from shuai-z/fix-portalloc

Fix corner cases in ipallocator and portallocator
Remove obsolete comments
In the below comment line, already codes for log exists so
following comment is obsolete.
// TODO log

Signed-off-by: Daehyeok Mun <daehyeok@gmail.com>
Merge pull request #9197 from somaopensource/remove_obsolete_comment

Remove obsolete comments