[dd-ctl] Fix installation

By toying with the new CI we discover that:
Commit 075529f472 gets into an endless
loop:
    WARNING:root:Could not get moodle SAML2 crt certificate. Retrying...
See: https://ci.dd-work.space/#/builders/4/builds/62/steps/8/logs/stdio

But by reverting 52f99c38bb it works as
expected.
See: https://ci.dd-work.space/#/builders/4/builds/67/steps/8/logs/stdio

Upon investigation, we were not waiting for moodle to be fully up
because 'healthy' is a substring of 'unhealthy' and grep wasn't taking
that into account.

dd-ctl

@@ -500,7 +500,7 @@ saml_certificates(){
 wait_for_moodle(){
 	echo "Waiting for system to be fully up before customizing... It can take some minutes..."
 	echo " (you can monitorize install with: docker logs dd-apps-moodle --follow"
-	while ! docker inspect -f '{{.State.Health.Status}}' dd-apps-moodle | grep -q "healthy"; do     sleep 2; done
+	while ! docker inspect -f '{{.State.Health.Status}}' dd-apps-moodle | grep -q "^healthy$"; do     sleep 2; done
 }
 
 upgrade_moodle(){