Description of problem:
According to Replace controller instructions from OSP15-beta documentation
https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/15-beta/html-single/director_installation_and_usage/index#replacing-controller-nodes

4  Perform a backup of the undercloud databases:

(undercloud) $ mkdir /home/stack/backup
(undercloud) $ sudo mysqldump --all-databases --quick --single-transaction | gzip > /home/stack/backup/dump_db_undercloud.sql.gz

(undercloud) [stack@undercloud-0 ~]$ sudo mysqldump --all-databases --quick --single-transaction | gzip > /home/stack/backup/dump_db_undercloud.sql.gz
mysqldump: Got error: 1102: "Incorrect database name '#mysql50#.config'" when selecting the database
(undercloud) [stack@undercloud-0 ~]$ echo $?
0

Version-Release number of selected component (if applicable):
OSP15-compose - RHOS_TRUNK-15.0-RHEL-8-20190722.n.1
python3-openstackclient-3.18.0-0.20190312140834.6868499.el8ost.noarch
openstack-tripleo-common-containers-10.8.1-0.20190719020421.f2a2fd2.el8ost.noarch
openstack-heat-monolith-12.0.1-0.20190704050403.bf16acc.el8ost.noarch
puppet-openstack_extras-14.4.1-0.20190420090934.6b1b687.el8ost.noarch
puppet-openstacklib-14.4.1-0.20190420125152.3719ca1.el8ost.noarch
openstack-tripleo-image-elements-10.4.1-0.20190705161217.2c8a6a5.el8ost.noarch
openstack-tripleo-validations-10.5.1-0.20190719021545.f3fe208.el8ost.noarch
openstack-heat-agents-1.8.1-0.20190523210450.1e15344.el8ost.noarch
openstack-heat-api-12.0.1-0.20190704050403.bf16acc.el8ost.noarch
openstack-tripleo-common-10.8.1-0.20190719020421.f2a2fd2.el8ost.noarch
openstack-selinux-0.8.19-0.20190606150404.06faac7.el8ost.noarch
python-openstackclient-lang-3.18.0-0.20190312140834.6868499.el8ost.noarch
openstack-tripleo-puppet-elements-10.3.2-0.20190710165331.c89fe3c.el8ost.noarch
openstack-heat-engine-12.0.1-0.20190704050403.bf16acc.el8ost.noarch
openstack-tripleo-heat-templates-10.6.1-0.20190722170519.014b20c.el8ost.noarch
python3-openstacksdk-0.27.0-0.20190405091843.4174082.el8ost.noarch
openstack-heat-common-12.0.1-0.20190704050403.bf16acc.el8ost.noarch

How reproducible:
always

Steps to Reproduce:
1.Perform a backup of the undercloud databases: 
2.sudo yum -y install mariadb
3.sudo mysqldump --all-databases --quick --single-transaction | gzip > /home/stack/backup/dump_db_undercloud.sql.gz

Actual results:
mysqldump: Got error: 1102: "Incorrect database name '#mysql50#.config'" when selecting the database


Expected results:


Additional info: