REGTEST: Add some informatoin to test results.

When the reg tests fail, it may be useful to display additional information
coming from varnishtest, especially when this latter aborts.
In such case, the test output may be made of lines prefixed by "*     diag"
string.

scripts/run-regtests.sh

@@ -454,7 +454,7 @@ if [ -d "${TESTDIR}" ]; then
     cat <<- EOF | tee -a "$TESTDIR/failedtests.log"
 $(echo "###### $(cat "$i/INFO") ######")
 $(echo "## test results in: \"$i\"")
-$(grep -- ^---- "$i/LOG")
+$(grep -E -- "^(----|\*    diag)" "$i/LOG")
 EOF
   done' sh {} +
 fi