multimds: fuse_default_permissions = 0 for kernel build test

This can reduce the test time becuase it avoids sending getattr
request whenever the kernel checks inode permission.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Merge pull request #22 from ceph/wip-fuse-permission

multimds: fuse_default_permissions = 0 for kernel build test