Add virsh blockcopy/blockpull/blockjob commands function wrapper

Signed-off-by: Yanbing Du <ydu@redhat.com>
Add configuration for virsh blockcopy testing

Note, for max bandwidth testing, there's a bug(BZ#927156), and for
invalid timeout testing, there's a bug(BZ#927495).

Signed-off-by: Yanbing Du <ydu@redhat.com>
Add test module for virsh blockcopy testing

Introduce virsh blockcopy testing:

    1. Positive testing
        1.1 Copy a disk to a new image file.
        1.2 Reuse existing destination copy.
        1.3 Valid timeout and bandwidth test.
        1.4 Other valid options test
    2. Negative testing
        2.1 Copy a disk to a non-exist file.
        2.2 Copy a disk with invalid options.
        2.3 Do blcok copy for a persistent domain.

Signed-off-by: Yanbing Du <ydu@redhat.com>