crash-reporter: crash_sender: strip dashes from clientids

Since Chrome has started preserving the dashes, we have to strip them
ourselves when uploading reports.

BUG=chromium:398217
BUG=391338
TEST=`cbuildbot x86-generic-full` passes

Change-Id: I795fb7fd6feae3c4f97829a849f0271c61e84490
Reviewed-on: https://chromium-review.googlesource.com/212229


Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>