PMM-15195 Fixes for MySQL.

[JiriCtvrtka]

https://jira.percona.com/browse/PMM-15195

PMM PR: percona/pmm#5648
MySQL Exporter PR: percona/mysqld_exporter#387
Percona Toolkit PR: percona/percona-toolkit#1152

[JNKPercona]

Server docker: perconalab/pmm-server-fb:PR-4479-8553b09
Client docker: perconalab/pmm-client-fb:PR-4479-8553b09
Watchtower docker: perconalab/pmm-watchtower-fb:PR-4479-8553b09
Client tarball: https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-8553b09.tar.gz
Staging instance: https://pmm.cd.percona.com/job/pmm3-aws-staging-start/parambuild/?DOCKER_VERSION=perconalab/pmm-server-fb:PR-4479-8553b09&CLIENT_VERSION=https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-8553b09.tar.gz

[JNKPercona]

API tests have succeded: https://pmm.cd.percona.com/job/pmm3-api-tests/6788/

[JNKPercona]

Server docker: perconalab/pmm-server-fb:PR-4479-abda1c8
Client docker: perconalab/pmm-client-fb:PR-4479-abda1c8
Watchtower docker: perconalab/pmm-watchtower-fb:PR-4479-abda1c8
Client tarball: https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-abda1c8.tar.gz
Staging instance: https://pmm.cd.percona.com/job/pmm3-aws-staging-start/parambuild/?DOCKER_VERSION=perconalab/pmm-server-fb:PR-4479-abda1c8&CLIENT_VERSION=https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-abda1c8.tar.gz

[JNKPercona]

API tests have succeded: https://pmm.cd.percona.com/job/pmm3-api-tests/7077/

[JNKPercona]

Server docker: perconalab/pmm-server-fb:PR-4479-62a8d82
Client docker: perconalab/pmm-client-fb:PR-4479-62a8d82
Watchtower docker: perconalab/pmm-watchtower-fb:PR-4479-62a8d82
Client tarball: https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-62a8d82.tar.gz
Staging instance: https://pmm.cd.percona.com/job/pmm3-aws-staging-start/parambuild/?DOCKER_VERSION=perconalab/pmm-server-fb:PR-4479-62a8d82&CLIENT_VERSION=https://s3.us-east-2.amazonaws.com/pmm-build-cache/PR-BUILDS/pmm-client/pmm-client-PR-4479-62a8d82.tar.gz

[JNKPercona]

API tests have succeded: https://pmm.cd.percona.com/job/pmm3-api-tests/7090/