domain_cgroup.c: add virDomainCgroupSetupDomainBlkioParameters()

domain_cgroup.c: add virDomainCgroupSetupDomainBlkioParameters()

After the introduction of virDomainDriverMergeBlkioDevice() in a
previous patch, it is now clear that lxcDomainSetBlkioParameters() and
qemuDomainSetBlkioParameters() uses the same loop to set cgroup
blkio parameter of a domain.

Avoid the repetition by adding a new helper called
virDomainCgroupSetupDomainBlkioParameters().

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>