Pin fpm to 1.11.0

fpm 1.12.0 adds an unintended runtime dependency on git, which should be
fixed in a future release. Pin fpm for now since installing git has its
own side effects, such as installing less and changing the default pager
on systems where less isn't available by default.

builder/Dockerfile.opensuse-15

@@ -66,7 +66,8 @@ RUN zypper --non-interactive --gpg-auto-import-keys -n install \
 
 RUN pip install awscli
 
-RUN gem install fpm && \
+# Pin fpm to avoid git dependency in 1.12.0
+RUN gem install fpm:1.11.0 && \
     ln -s /usr/bin/fpm.ruby2.5 /usr/local/bin/fpm
 
 RUN chmod 0777 /opt