test-execute: cleanup

This makes rename the test units by a consistent naming scheme,
add several logs, and sort internal functions.
No functional change.

test/test-execute/exec-bindpaths.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=Test for BindPaths= and BindReadOnlyPaths=
+
+[Service]
+Type=oneshot
+# Create a file in /tmp/test-exec-bindpaths
+ExecStart=/bin/sh -c 'touch /tmp/test-exec-bindpaths/thisisasimpletest'
+# Then, the file can be access through /tmp
+ExecStart=/bin/sh -c 'test -f /tmp/thisisasimpletest'
+# Also, through /tmp/test-exec-bindreadonlypaths
+ExecStart=/bin/sh -c 'test -f /tmp/test-exec-bindreadonlypaths/thisisasimpletest'
+# The file cannot modify through /tmp/test-exec-bindreadonlypaths
+ExecStart=/bin/sh -x -c '! touch /tmp/test-exec-bindreadonlypaths/thisisasimpletest'
+# Cleanup
+ExecStart=/bin/sh -c 'rm /tmp/thisisasimpletest'
+BindPaths=/tmp:/tmp/test-exec-bindpaths
+BindReadOnlyPaths=/tmp:/tmp/test-exec-bindreadonlypaths