Revert "kvm: set volume ID as guest device serial ID."

Setting serial parameter to -device was not right path.
This reverts commit 79e0149c711b57518e0f789128f7f3733e59b8a9.
kvm: Set serial parameter to -drive option.

-device <driver> sometime did not accept serial parameter depends on
the driver type. serial parameter in -drive seems to be available as common.
Merge pull request #349 from axsh/fix-kvm-serial-parameter

Fix kvm serial parameter to set as part of -drive.