Merge branch 'tidy-runall.sh-environment-variables' into 'master'

Tidy runall.sh environment variables

See merge request isc-projects/bind9!18

diff --cc bin/tests/system/Makefile.in
Simple merge

diff --cc bin/tests/system/README
Simple merge

diff --cc bin/tests/system/conf.sh.in
Simple merge

diff --cc bin/tests/system/run.sh
Simple merge

diff --cc bin/tests/system/runall.sh
Simple merge