ci: Set DEBIAN_FRONTEND=noninteractive

Also fix travis environment variables for this build

Previously the resulting env was:

FILE_ENV="./ci/test/00_setup_env_native_tsan.sh" TEST_RUNNER_EXTRA="--exclude feature_block" #= Not= enough= memory= on= travis= machines=

ci/test/00_setup_env.sh

@@ -40,6 +40,8 @@ export DOCKER_NAME_TAG=${DOCKER_NAME_TAG:-ubuntu:18.04}
 # Randomize test order.
 # See https://www.boost.org/doc/libs/1_71_0/libs/test/doc/html/boost_test/utf_reference/rt_param_reference/random.html
 export BOOST_TEST_RANDOM=${BOOST_TEST_RANDOM:-1}
+# See man 7 debconf
+export DEBIAN_FRONTEND=noninteractive
 export CCACHE_SIZE=${CCACHE_SIZE:-100M}
 export CCACHE_TEMPDIR=${CCACHE_TEMPDIR:-/tmp/.ccache-temp}
 export CCACHE_COMPRESS=${CCACHE_COMPRESS:-1}