reader_permit: release_base_resources(): also update _resources

If the permit was admitted, _base_resources was already accounted in
_resource and therefore has to be deducted from it, otherwise the permit
will think it leaked some resources on destruction.

Test:
dtest(repair_additional_test.py.test_repair_one_missing_row_diff_shard_count)

Refs: #9751
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20220119132550.532073-1-bdenes@scylladb.com>
(cherry picked from commit a65b38a)

reader_concurrency_semaphore.cc

@@ -250,6 +250,10 @@ class reader_permit::impl
     }
 
     void release_base_resources() noexcept {
+        if (_base_resources_consumed) {
+            _resources -= _base_resources;
+            _base_resources_consumed = false;
+        }
         _semaphore.signal(std::exchange(_base_resources, {}));
     }