test: exit on first failing subtest

Let's take a step back and revert back to the original behavior where we
exit on a first failing subtest. The current behavior makes fishing out the
failing test details quite unpleasant, and in certain situations the
journal may even be rotated away so we end up with no actionable logs.

test/units/test-control.sh

@@ -8,7 +8,6 @@ fi
 
 declare -i _CHILD_PID=0
 _PASSED_TESTS=()
-_FAILED_TESTS=()
 
 # Like trap, but passes the signal name as the first argument
 _trap_with_sig() {
@@ -57,7 +56,7 @@ _wait_harder() {
 _show_summary() {(
     set +x
 
-    if [[ ${#_PASSED_TESTS[@]} -eq 0 && ${#_FAILED_TESTS[@]} -eq 0 ]]; then
+    if [[ ${#_PASSED_TESTS[@]} -eq 0 ]]; then
         echo >&2 "No tests were executed, this is most likely an error"
         exit 1
     fi
@@ -67,16 +66,6 @@ _show_summary() {(
     for t in "${_PASSED_TESTS[@]}"; do
         echo "$t"
     done
-
-    if [[ "${#_FAILED_TESTS[@]}" -ne 0 ]]; then
-        printf "FAILED TESTS: %3d:\n" "${#_FAILED_TESTS[@]}"
-        echo   "------------------"
-        for t in "${_FAILED_TESTS[@]}"; do
-            echo "$t"
-        done
-    fi
-
-    [[ "${#_FAILED_TESTS[@]}" -eq 0 ]]
 )}
 
 # Like run_subtests, but propagate specified signals to the subtest script
@@ -100,7 +89,7 @@ run_subtests_with_signals() {
         : "--- $subtest BEGIN ---"
         "./$subtest" &
         _CHILD_PID=$!
-        _wait_harder "$_CHILD_PID" && _PASSED_TESTS+=("$subtest") || _FAILED_TESTS+=("$subtest")
+        _wait_harder "$_CHILD_PID" && _PASSED_TESTS+=("$subtest") || return 1
         : "--- $subtest END ---"
     done
 
@@ -124,7 +113,7 @@ run_subtests() {
         fi
 
         : "--- $subtest BEGIN ---"
-        "./$subtest" && _PASSED_TESTS+=("$subtest") || _FAILED_TESTS+=("$subtest")
+        "./$subtest" && _PASSED_TESTS+=("$subtest") || return 1
         : "--- $subtest END ---"
     done