ram-allocation-ratio is set too high

[James Troup]

ram-allocation-ratio defaults to 1.5 but, IMO, this is dangerous and
can (and has for us) lead to OOMs kills on compute hosts.

Please consider lowering this to 1 or 0.9. Please also consider
adding some text to config.yaml which talks about how this ratio will need to be
adjusted in a converged or hyper-converged architecture.

[Frode Nordahl (fnordahl)]

Moving task to upstream OpenStack Charms project

[Frode Nordahl (fnordahl)]

https://review.openstack.org/#/c/640541/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/640541
Committed: https://git.openstack.org/cgit/openstack/charm-nova-cloud-controller/commit/?id=fe0ba3b8830bb14ca479f0c43ea00b5b1fbedeb0
Submitter: Zuul
Branch: master

commit fe0ba3b8830bb14ca479f0c43ea00b5b1fbedeb0
Author: Frode Nordahl <email address hidden>
Date: Fri Mar 1 22:53:26 2019 +0100

    Adjust default of ``ram-allocation-ratio`` configuration option

    In modern hyper-converged architectures the upstream default of
    1.5 does not really fit.

    Set to 0.98 to give some headroom on the compute nodes and add
    a note about the potential need to adjust this value further.

    Change-Id: I64e3379686128dd7f222bdfae133a6c90e8f3ef0
    Closes-Bug: #1818234