linux: Support 4.10 format for empty Groups: lines in /proc/pid/status
linux: Support 4.10 format for empty Groups: lines in /proc/pid/status

The Groups: line unfortunately always had a trailing space, but Linux
4.10 takes this to a new level by including a trailing space even when
no groups are present. See commit f7a5f132b447,
linux-4.10.10/fs/proc/array.c task_state().

Bug: crashpad:30
Test: crashpad_util_test ProcessInfo.Pid1
Change-Id: If498abd929b27c7f28b69144e7c4928b1626acdb
Reviewed-on: https://chromium-review.googlesource.com/477070
Reviewed-by: Joshua Peraza <f5809a5e35ec7e1bd0e25cb0a0b68bb433cf6f17@chromium.org>

chromium/crashpad,atom/crashpad,atom/crashpad,chromium/crashpad,atom/crashpad,chromium/crashpad