Drop Release label in favor of OSBS release_bump plugin.

OSBS can automatically bump the release number, for that
we just need to drop the label from the Dockerfile

See https://pagure.io/ContainerSIG/container-sig/issue/1

Signed-off-by: Clement Verna <cverna@tutanota.com>

Dockerfile

@@ -10,7 +10,6 @@ LABEL MAINTAINER "Augusto Caringi" <acaringi@redhat.com>
 
 ENV NAME=cassandra \
     VERSION=0 \
-    RELEASE=3 \
     ARCH=x86_64 \
     SUMMARY="Cassandra is an OpenSource database for high-scale application" \
     DESCRIPTION="Cassandra is a partitioned row store. Rows are organized \
@@ -26,7 +25,6 @@ LABEL summary="$SUMMARY" \
       com.redhat.component="$NAME" \
       name="$FGC/$NAME" \
       version=0 \
-      release="$RELEASE.$DISTTAG" \
       architecture="$ARCH" \
       usage="docker run cassandra" \
       help="help.1"