[gutil] remove unused code from walltime.{h,cc}

While working on the `kudu diagnose parse_metrics` CLI tool, I noticed
some functions in walltime were unused.  With that and questioning
why to re-implement libc's functionality at all, I removed the unused
code: WallTime_Parse_Timezone() and a few other local functions.

There are no functional changes in this patch.

Change-Id: Ieddb6d34c047450f4e5cf445d290e965580c4ed5
Reviewed-on: http://gerrit.cloudera.org:8080/18972
Tested-by: Kudu Jenkins
Reviewed-by: Yifan Zhang <chinazhangyifan@163.com>
2 files changed