BUG/MINOR: stick-tables: abort startup on stk_ctr pool creation failure

BUG/MINOR: stick-tables: abort startup on stk_ctr pool creation failure

Since 3.3 with commit 945aa0ea82 ("MINOR: initcalls: Add a new initcall
stage, STG_INIT_2"), stkt_late_init() calls stkt_create_stk_ctr_pool()
but doesn't check its return value, so if the pool creation fails, the
process still starts, which is not correct. This patch adds a check for
the return value to make sure we fail to start in this case. This was
not an issue before 3.3 because the function was called as a post-check
handler which did check for errors in the returned values.