crash-reporter: fix linter issues

Fixed various issues reported by cpplint.py when run on
src/platform2/crash-reporter.

BUG=None
TEST=FEATURES=test emerge-link crash-reporter
cpplint.py `find crash-reporter/* | grep "\.cc\|\.h"`

Change-Id: If874b3dbf539d2dd22cf740a0d3523225d1c61a7
Reviewed-on: https://chromium-review.googlesource.com/210418


Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>