LU-14905 lfsck: linkEA overflow handling fix

LU-14905 lfsck: linkEA overflow handling fix

An absent link in EA is not an issue and not to be fixed if EA is
overflowed. lfsck should not report it is an issue if there is no
space for this link, and should not report it is fixed whereas it
is not (linkea_add_buf() returns 0 if so without having a new entry
added into EA and lfsck_namespace_assistant_handler_p1() later
reports it is repaired).

HPE-bug-id: LUS-8810
Signed-off-by: Vitaly Fertman <vitaly.fertman@hpe.com>
Change-Id: Iba1549045c8c3889adf55c99cdd88756e5643073
Reviewed-on: https://es-gerrit.dev.cray.com/158706
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Alexander Zarochentsev <c17826@cray.com>
Tested-by: Jenkins Build User <nssreleng@cray.com>
Reviewed-on: https://review.whamcloud.com/44469
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>