domain_cgroup.c: update domain after setting blkio.weight

domain_cgroup.c: update domain after setting blkio.weight

Commit ac87d3520ad5 consolidated common cgroup code between the QEMU and
lxc drivers in domain_cgroup.c. In this process, in
virDomainCgroupSetupDomainBlkioParameters(), a call to
virCgroupGetBlkioWeight() went missing.

The result is that 'virsh blkiotune' is setting the blkio.weight for the
guest in the host cgroup, but not on the domain XML, because
virCgroupGetBlkioWeight() is also used to write the blkio.weight value
in the domain object.

Fix it by adding the virCgroupGetBlkioWeight() call in the
virDomainCgroupSetupDomainBlkioParameters() helper.

Fixes: ac87d3520ad542d558854a72b0ae0a81fddc6747
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1941407
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>