Remove usage of zypper

There is no zypper anymore in bci micro based containers.

tests/test_postfix.py

@@ -28,13 +28,9 @@
 
 
 CONTAINERFILE_POSTFIX_WITH_LDAP_ENABLED = """
-RUN set -euo pipefail; \
-zypper -n in --no-recommends find openldap2 openldap2-client; \
-zypper -n clean; \
-rm -rf /var/log/{lastlog,tallylog,zypper.log,zypp/history,YaST2}
-
 # TODO: move postfix & openldap container files to bci-dockerfile-generator
-RUN curl -Lsf -o - https://github.com/thkukuk/containers-mailserver/archive/refs/heads/master.tar.gz | tar  --no-same-permissions --no-same-owner -xzf - && \
+RUN set -euo pipefail; \
+    curl -Lsf -o - https://github.com/thkukuk/containers-mailserver/archive/refs/heads/master.tar.gz | tar  --no-same-permissions --no-same-owner -xzf - && \
     cd containers-mailserver-master/openldap && \
     cp -r ldif /entrypoint/ && \
     cp slapd.init.ldif /entrypoint/ && \