Drop mesos driver

The coe mesos has not been maitenaned for quite some
time and hasn't got much attetion from the community
in general. As discussed in the mailing list [1] we
are dropping for now.

In this patch, we start by removing the mesos driver
and its test cases. This part of the code has no impact
for other drivers. Then we can clean up mesos references
that affect the API.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-December/026230.html

Conflicts:
	lower-constraints.txt
	tox.ini

Change-Id: Ied76095f1f1c57c6af93d1a6094baa6c7cc31c9b