qemu: Pass correct qemuCaps to virDomainDeviceDefPostParse

qemu: Pass correct qemuCaps to virDomainDeviceDefPostParse

Since qemuDomainDeviceDefPostParse callback requires qemuCaps, we need
to make sure it gets the capabilities stored in the domain's private
data if the domain is running. Passing NULL may cause QEMU capabilities
probing to be triggered in case QEMU binary changed in the meantime.
When this happens while a running domain object is locked, QMP event
delivered to the domain before QEMU capabilities probing finishes will
deadlock the event loop.

QEMU capabilities lookup (via domainPostParseDataAlloc callback) is
hidden inside virDomainDeviceDefPostParseOne with no way to pass
qemuCaps to virDomainDeviceDef* functions. This patch fixes all
remaining paths leading to virDomainDeviceDefPostParse.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>