commandline: fix up docstring lint warnings
commandline: fix up docstring lint warnings

BUG=chromium:327969
TEST=`cros lint lib/commandline.py` is clean

Change-Id: I8abe0208b6fa00fec38f0738779f60f4bfd9ea7e
Reviewed-on: https://chromium-review.googlesource.com/180110
Commit-Queue: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite