ci: Install findutils in build environment

The *findutils* package is needed for the `find` command, which is used
at the end of the CI pipelines to remove the `sudo-pass` vault files.

ci/Dockerfile

@@ -4,6 +4,7 @@ RUN useradd -l -u 3000018 jenkins
 
 RUN dnf install -y \
 	ansible \
+	findutils \
 	krb5-workstation \
 	openssh-clients \
 	python3-dns \