Add trailing slash to COPY target dir

Docker build fails on the target with "not a directory", unless it includes
a trailing slash.
diff --git a/docker/centos7-image.docker b/docker/centos7-image.docker
index f9b1e16..fc82d4d 100644
--- a/docker/centos7-image.docker
+++ b/docker/centos7-image.docker
@@ -44,4 +44,4 @@
 WORKDIR $CASSANDRA_DIR
 RUN ant maven-ant-tasks-retrieve-build
 
-COPY build-rpms.sh $BUILD_HOME
+COPY build-rpms.sh $BUILD_HOME/
diff --git a/docker/jessie-image.docker b/docker/jessie-image.docker
index 3de19d2..80bce88 100644
--- a/docker/jessie-image.docker
+++ b/docker/jessie-image.docker
@@ -39,5 +39,4 @@
 WORKDIR ${CASSANDRA_DIR}
 RUN ant maven-ant-tasks-retrieve-build
 
-COPY build-debs.sh $BUILD_HOME
-
+COPY build-debs.sh $BUILD_HOME/