Improve github test driver script.

- use a trap to always output any failed regress logs (since the script
   sets -e, the existing log output is never invoked).
 - pass LTESTS and SKIP_LTESTS when re-running with sshd options (eg.
   UsePAM).

.github/run_test.sh

@@ -6,28 +6,29 @@
 
 set -ex
 
-if [ -z "${LTESTS}" ]; then
-    make ${TEST_TARGET} SKIP_LTESTS="${SKIP_LTESTS}"
-    result=$?
-else
-    make ${TEST_TARGET} SKIP_LTESTS="${SKIP_LTESTS}" LTESTS="${LTESTS}"
-    result=$?
-fi
-
-if [ ! -z "${SSHD_CONFOPTS}" ]; then
-    echo "rerunning tests with TEST_SSH_SSHD_CONFOPTS='${SSHD_CONFOPTS}'"
-    make t-exec TEST_SSH_SSHD_CONFOPTS="${SSHD_CONFOPTS}"
-    result2=$?
-    if [ "${result2}" -ne 0 ]; then
-        result="${result2}"
-    fi
-fi
-
-if [ "$result" -ne "0" ]; then
+output_failed_logs() {
     for i in regress/failed*; do
+        if [ -f "$i" ]; then
             echo -------------------------------------------------------------------------
             echo LOGFILE $i
             cat $i
             echo -------------------------------------------------------------------------
+        fi
     done
+}
+trap output_failed_logs 0
+
+if [ -z "${LTESTS}" ]; then
+    make ${TEST_TARGET} SKIP_LTESTS="${SKIP_LTESTS}"
+else
+    make ${TEST_TARGET} SKIP_LTESTS="${SKIP_LTESTS}" LTESTS="${LTESTS}"
+fi
+
+if [ ! -z "${SSHD_CONFOPTS}" ]; then
+    echo "rerunning t-exec with TEST_SSH_SSHD_CONFOPTS='${SSHD_CONFOPTS}'"
+    if [ -z "${LTESTS}" ]; then
+        make t-exec SKIP_LTESTS="${SKIP_LTESTS}" TEST_SSH_SSHD_CONFOPTS="${SSHD_CONFOPTS}"
+    else
+        make t-exec SKIP_LTESTS="${SKIP_LTESTS}" LTESTS="${LTESTS}" TEST_SSH_SSHD_CONFOPTS="${SSHD_CONFOPTS}"
+    fi
 fi