[Sheriff] Disable flaky addressspace-serviceworker-basic.html

Disables the flaky test
  virtual/cors-rfc1918/http/tests/security/cors-rfc1918/
    addressspace-serviceworker-basic.html
on Linux.

TBR=nhiroki@chromium.org

BUG=chromium:988074
TEST=Made sure failure is OK. Failure shows up as
     "The test ran as expected (0 passed, 1 didn't)."

Change-Id: I5a49ca60b7ab3bc1b15f96ffad456be65c9e35a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1722543
Commit-Queue: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681792}

third_party/blink/web_tests/TestExpectations

@@ -6384,3 +6384,4 @@ crbug.com/988298 [ Linux ] http/tests/devtools/extensions/extensions-panel.js [
 
 # Sheriff 2019-07-29
 crbug.com/937811 [ Win Release ] http/tests/devtools/elements/shadow/elements-panel-shadow-selection-on-refresh-3.js [ Pass Failure Timeout ]
+crbug.com/988074 [ Linux ] virtual/cors-rfc1918/http/tests/security/cors-rfc1918/addressspace-serviceworker-basic.html [ Pass Failure ]