LU-14692 tests: restore sanity/312 to always_except

LU-14692 tests: restore sanity/312 to always_except

The sanity test_312 was incorrectly removed from ALWAYS_EXCEPT.

Fixes: eaae465556 ("LU-14692 tests: allow FID_SEQ_NORMAL for MDT0000")
Test-Parameters: trivial testlist=sanity fstype=zfs
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I6e8ed42561809b28fd6d5b4f7ee1104080ebe756
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49720
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>