test: don't use /skipped for subtests

Since, at least the old framework, checks for the presence of the file
at the end and marks the whole test as skipped if it exists.

Resolves: systemd/systemd-centos-ci#728

test/units/TEST-04-JOURNAL.bsod.sh

@@ -4,12 +4,12 @@ set -eux
 set -o pipefail
 
 if systemd-detect-virt -cq; then
-    echo "This test requires a VM, skipping the test" | tee --append /skipped
+    echo "This test requires a VM, skipping the test"
     exit 0
 fi
 
 if [[ ! -x /usr/lib/systemd/systemd-bsod ]]; then
-    echo "systemd-bsod is not installed, skipping the test" | tee --append /skipped
+    echo "systemd-bsod is not installed, skipping the test"
     exit 0
 fi
 

test/units/TEST-17-UDEV.credentials.sh

@@ -5,7 +5,7 @@ set -eux
 set -o pipefail
 
 if [[ $(systemctl is-enabled systemd-udev-load-credentials.service) == not-found ]]; then
-    echo "Missing systemd-udev-load-credentials.service" >>/skipped
+    echo "Missing systemd-udev-load-credentials.service"
     exit 0
 fi