chimera: protect list initialization from FS inconsistencies

we observe that in some situations nlink count get out of
sync. As this is a bug by itself, protect directory listing
from from invalid initial capacity initialization.

Acked-by: Karsten Schwank
Target: master
Require-book: no
Require-notes: no
(cherry picked from commit d325d16e29e7454f3ecc916c0b54a42feb6903ee)
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Merge pull request #1020 from kofemann/no-IAE-on-readdir-2.7

chimera: protect list initialization from FS inconsistencies