rbd functionality is enabled only on machines with supported libc version.

See merge request !1209

The mariadb/proxysql service automatically start when repman shut it down then
repman cannot check if service was correcty stopped because it's already up.
Stop a service will not work too.

It should be possible to add 2 or more cluster in the same instance

Rarely used https backend was missing the backend Via additions, thus it was
not transmitted there.

This reverts commit e7b48c0b.

This reverts commit 201d238a.

See merge request !1212

This is a fixup of bddc5491.

See merge request !1188

Now, with the `chain` option, you can source a chain of activate script
created by the macro.

In addition, the `deactivate` function will return to the initial environment.

The `message` option allows to write a message that will be displayed when sourcing the script.

The `environment` option allows you to write your own environment variables for the virtual environment.
To use it:
environment =
  <env-name> = <env-value>

See merge request !1211

MarkupSafe 1.0 is not compatible with Python 3.8

See merge request nexedi/slapos!1208