LU-15502 llite: set default LMV hash type with 2.12 MDS

LU-15502 llite: set default LMV hash type with 2.12 MDS

If default LMV hash type is CRUSH, or unset, it should be converted
to fnv_16_64, because 2.12 MDS doesn't understand this.

Fix LMV_HASH_FLAG_KNOWN to match actual known flags.

Test-Parameters: testlist=sanity env=ONLY=300 mdtcount=2 serverversion=2.12 serverdistro=el7.9
Fixes: 0a1cf8da8069 ("LU-11025 dne: introduce new directory hash type: "crush")
Fixes: bb60caa1c6e7 ("LU-14459 lmv: change default hash type to crush")
Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Ie2ad5a456040dcd01bc2c5ab96db52bf944abbd2