Fix broken chef/berkshelf install in docker images

Set a specific version for the ruby gem "public_suffix", required by chef/berkshelf,
to be compatible with the used version of ruby (2.5.0).

Signed-off-by: Vasyl Razinkov <vasyl.razinkov@est.tech>
Change-Id: I963a60206cb1f22296fcb5a9f763f326f629f077
Issue-ID: SDC-4139
diff --git a/openecomp-be/dist/sdc-onboard-backend-docker/artifacts/Dockerfile b/openecomp-be/dist/sdc-onboard-backend-docker/artifacts/Dockerfile
index f6ed6c4..a9ab7a9 100644
--- a/openecomp-be/dist/sdc-onboard-backend-docker/artifacts/Dockerfile
+++ b/openecomp-be/dist/sdc-onboard-backend-docker/artifacts/Dockerfile
@@ -13,6 +13,7 @@
         libffi-dev \
         libxml2-dev \
         libressl-dev && \
+    gem install public_suffix -v 4.0.7 --no-document && \
     gem install multipart-post -v 2.2.0 --no-document && \
     gem install chef:13.8.5 berkshelf:6.3.1 io-console:0.4.6 etc webrick --no-document && \
     gem cleanup && \