virtgpu: remove redundant task_comm copying

Remove redundant task name copying because:

1. task->comm is already NUL-terminated
2. virtio_gpu_context_create() trims passed dbgname anyway

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: http://patchwork.freedesktop.org/patch/msgid/588612bbc672e8b598e10f79fcbc041122e844ba.1504202471.git.mirq-linux@rere.qmqm.pl


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>