qemu.test: fix python3 compatibility issue

1. for case block_discard and physical_resources_check
Signed-off-by: NXueqiang Wei <xuwei@redhat.com>

qemu/tests/block_discard.py

@@ -32,7 +32,7 @@ def run(test, params, env):
         """
         Get latest scsi disk which emulated by scsi_debug module.
         """
-        scsi_disk_info = process.system_output("lsscsi").splitlines()
+        scsi_disk_info = process.system_output("lsscsi").decode().splitlines()
         scsi_debug = [_ for _ in scsi_disk_info if 'scsi_debug' in _][-1]
         scsi_debug = scsi_debug.split()
         host_id = scsi_debug[0][1:-1]

qemu/tests/physical_resources_check.py

@@ -175,8 +175,8 @@ def run(test, params, env):
             test.error("Failed to get machine type from vm")
 
         machine_type_cmd = "%s -M ?" % utils_misc.get_qemu_binary(params)
-        machine_types = process.system_output(machine_type_cmd,
-                                              ignore_status=True)
+        machine_types = process.system_output(
+                machine_type_cmd, ignore_status=True).decode()
         machine_types = machine_types.split(':')[-1]
         machine_type_map = {}
         for machine_type in machine_types.splitlines():