LU-15910 llite: use max default EA size to get default LMV

LU-15910 llite: use max default EA size to get default LMV

Subdir mount will fetch ROOT default LMV and set it, but the default
EA size cl_default_mds_easize may not be set for MDT0 yet, because
it's updated upon getattr/enqueue, and if subdir mount is not on MDT0,
it may not be initialized yet. Use max EA size to fetch default
layout in ll_dir_get_default_layout().

Fixes: a162e24d2d ("LU-15910 llite: enforce ROOT default on subdir mount")
Fixes: 716ac65ef6 ("LU-15910 tests: skip sanity/413g for SSK")
Test-Parameters: env=SHARED_KEY=true,ONLY="413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413c 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413c 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413c 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413c 413g" testlist=sanity mdscount=1 mdtcount=2
Test-Parameters: env=SHARED_KEY=true,ONLY="413b 413c 413g" testlist=sanity mdscount=1 mdtcount=2
Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I3c762cd371a80c2bea12d7fdbc16c6b14b3214e6
Reviewed-on: https://review.whamcloud.com/47937
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>