NFS4: Cleanup FATTR4_WORD0_FS_LOCATIONS after decoding success

Commit 1ca843a2 "nfs: Fix GETATTR bitmap verification" has check
the bitmap after decoding success, but decode_attr_fs_locations forgets
cleanup the FATTR4_WORD0_FS_LOCATIONS bits.

decode_getfattr_attrs always return -EIO when meeting FS_LOCATIONS now.

ls: cannot access /mnt/referal: Input/output error
ls: cannot access /mnt/replicas: Input/output error
total 32
drwxr-xr-x. 7 root root 8192 Nov 16 20:36 pnfs
??????????? ? ?    ?       ?            ? referal
??????????? ? ?    ?       ?            ? replicas

v2: clear the bit earlier

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>