ctdb-build: Enable some standard event scripts if none are enabled

ctdb-build: Enable some standard event scripts if none are enabled

CTDB needs the legacy/00.ctdb event script to be able to function
properly.  If this script is not enabled then assume a first-time
install or an upgrade to a version that requires events scripts to be
enabled via symlinks.  In these cases enable this script and other
commonly used scripts.

Only do this for a direct install.  If DESTDIR is being used then
assume a package is being built and let the packager handle this case.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>