runqemu: chmod 0o777 for lockdir

runqemu: chmod 0o777 for lockdir

Multi-users may run qemu on the same host, all of them should be able to
create or remove lock in lockdir, so set lockdir's mode to 0o777.

Note, os.mkdir()'s mode is default to 0o777, but the current umask value is
first masked out, so use os.chmod() to set it.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>