Add rpm build drone pipeline step

.drone.yml

@@ -3,8 +3,8 @@ type: docker
 name: default
 
 steps:
-- name: Build Ubuntu 20:04 deb package
-  image: ubuntu:20.04
+- name: Build Ubuntu deb package
+  image: ubuntu
   volumes:
   - name: deb_packages
     path: /debian
@@ -17,8 +17,8 @@ steps:
     - lch -v
     - cp lch_0.6.10_all.deb /debian
 
-- name: Build CentOS 7 rpm package
-  image: centos:7
+- name: Build CentOS rpm package
+  image: centos
   volumes: 
   - name: rpm_packages
     path: /root/rpmbuild/RPMS/noarch/