blockcommit: Add active commit test cases

Since libvirt 1.2.4, active commit is supported, add test case to
cover this.
After snapshot and blockcommit, check the backing chain in disk
xml via backingStore element.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add guest agent testing case

Active block commit will do fsfreeze when ga around, without ga it
also works but no fsfreeze.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add test cases for iscsi network disk

For testing blockcommit with iscsi network disk vm, update domain
xml with iscsi network disk with reset_domain function.

The test aim to test iscsi disk with full os, so after iscsi lun
created, convert vm disk to the lun backing store raw file on
server use qemu-img command.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add test cases for gluster network disk

Similar to previous commit ac65ca1 for iscsi network disk, convert
current vm os disk to gluster disk file, update vm xml and testing
snapshot and blockcommit.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add snpashot during active-commit negative case

When blockcommit without --pivot, block job will still be
active-commit, doing snapshot at this phase will fail.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add block disk type test cases

For block disk in vm, use connected iscsi block disk. Before
snapshot and block commit, setup iscsi env and copy vm os disk
to iscsi backing store file which will enable vm booted with
full os, then start vm and do testing.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Add file disk type with image on mounted nfs dir

Replace domain image with image file on mounted nfs dir, then
do snapshot and block commit testing.

Signed-off-by: Wayne Sun <gsun@redhat.com>
blockcommit: Use functions from utils_test sub-module

Split the reset_domain function and moved it to utils_test.libvirt
module. Then use new set_guest_agent and set_vm_disk for pre-test
configuration.

Signed-off-by: Wayne Sun <gsun@redhat.com>
Merge pull request #344 from waynesun09/active_blockcommit

blockcommit: Add active commit test cases