Travis: Turn off Tor's Sandbox in Chutney jobs

We need to set "Sandbox 0", until we fix sandbox errors that are
triggered by Ubuntu Xenial and Bionic. See 32722.

Part of 32240.

.travis.yml

@@ -22,6 +22,9 @@ env:
     - HARDENING_OPTIONS="--enable-expensive-hardening"
     ## We turn off asciidoc by default, because it's slow
     - ASCIIDOC_OPTIONS="--disable-asciidoc"
+    ## Turn off tor's sandbox in chutney, until we fix sandbox errors that are
+    ## triggered by Ubuntu Xenial and Bionic. See #32722.
+    - CHUTNEY_TOR_SANDBOX="0"
   matrix:
     ## This matrix entry is required, but it doesn't actually create any jobs
     -