virt: Allows filter only subtests specific for test type and Adds qemu_img and bridge_mode process to general_options. 

based on: https://github.com/autotest/virt-test/pull/754

virt: Allows filter only subtests specific for test type.

Test type: qemu, libvirt, openvswitch, libguestfs.
Adds parameter "--type-specific" to command run.
By adding this parameter run filter only type specific subtests for
list and for running the tests.

virt: Adds qemu_img and bridge_mode process to general_options.