Do not override CHROME_DEVEL_SANDBOX in tools/valgrind/valgrind_test.py
Do not override CHROME_DEVEL_SANDBOX in tools/valgrind/valgrind_test.py

Setting that variable to an empty string is not a supported way of disabling the
sandbox. tools/valgrind/chrome_tests.py is supposed to pass "--no-sandbox" which
takes care of that.

BUG=245376
TBR=jln@chromium.org, timurrrr@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/880023003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#313517}

chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,ltilve/chromium,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,hgl888/chromium-crosswalk,Chilledheart/chromium,ltilve/chromium,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Just-D/chromium-1,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,ltilve/chromium,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,ltilve/chromium,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,fujunwei/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,fujunwei/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,chuan9/chromium-crosswalk,ltilve/chromium,ltilve/chromium,ltilve/chromium,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,ltilve/chromium,Fireblend/chromium-crosswalk,fujunwei/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,ltilve/chromium,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk