qemu.tests: fix interface not assign issue

Interface is requried by copy related function in remote module when
used linklocal address, this fix split IP and interface to fix this issue.
And fix small typo issue too.

Signed-off-by: Xu Tian <xutian@redhat.com>
Merge pull request #180 from xutian/fix_ipv6_file_transfer

qemu.tests: fix interface not assign issue