LU-15850 mdt: pack default LMV in open reply

LU-15850 mdt: pack default LMV in open reply

Add flag MDS_OPEN_DEFAULT_LMV to indicate that default LMV should be
packed in open reply, otherwise if open fetches LOOKUP lock, client
won't know directory has default LMV, and in subdir creation default
LMV won't take effect.

Test-Parameters: clientversion=2.14 testlist=sanity mdtcount=4 mdscount=2 env=SANITY_EXCEPT="39l 134b 150b 160g 205a 208 230e 230p 270a 300g 807"
Test-Parameters: serverversion=2.14 testlist=sanity mdtcount=4 mdscount=2 env=SANITY_EXCEPT="65n 247f"
Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: If2300ca39f406169eff9eab8f973ca1c2bfc8202
Reviewed-on: https://review.whamcloud.com/47576
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>