[BUG] stick_table: the fix for the memory leak caused a regression

[BUG] stick_table: the fix for the memory leak caused a regression

(cherry picked from commit 61ba936e6858dfcf9964d25870726621d8188fb9)
[ note: the bug was finally not present in 1.5-dev but at least we
  have to reset store_count to be compatible with 1.4 ]

Commit d6e9e3b5e320b957e6c491bd92d91afad30ba638 caused recently created
entries to be removed as soon as they were created, breaking stickiness.
It is not clear whether a use-after-free was possible or not in this case.

This bug was reported by Ben Congleton and narrowed down by Hervé Commowick,
both of whom also tested the fix. Thanks to them !