Qemu>=5.0.0 bumped the default tb-cache size to 1GiB(from 32MiB)
and this made it difficult to run multiple guest VMs on systems
running with lower memory. With Libvirt>=8.0.0 it's possible to
configure lower tb-cache size.
Below config option is introduced to allow configure
TB cache size as per environment needs, this only
applies to 'virt_type=qemu':-
[libvirt]tb_cache_size
Also enable this flag in nova-next job.
[1] https://github.com/qemu/qemu/commit/600e17b26
[2] https://gitlab.com/libvirt/libvirt/-/commit/58bf03f85
Closes-Bug: #1949606
Implements: blueprint libvirt-tb-cache-size
Change-Id: I49d2276ff3d3cc5d560a1bd96f13408e798b256a
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