Fix blockstore returning garbage for unstable reads if there is an in-flight version

"In-flight" versions are added into dirty_db when writes are enqueued. And they
weren't ignored by subsequent reads even though they didn't have data location yet.
This bug was leading to test_heal.sh not passing sometimes with replicated setups.

src/blockstore_write.cpp

@@ -139,7 +139,7 @@ bool blockstore_impl_t::enqueue_write(blockstore_op_t *op)
             uint8_t *bmp_ptr = (uint8_t*)(dsk.clean_entry_bitmap_size > sizeof(void*) ? bmp : &bmp);
             uint32_t bit = op->offset/dsk.bitmap_granularity;
             uint32_t bits_left = op->len/dsk.bitmap_granularity;
-            while (!(bit % 8) && bits_left > 8)
+            while (!(bit % 8) && bits_left >= 8)
             {
                 // Copy bytes
                 bmp_ptr[bit/8] = ((uint8_t*)op->bitmap)[bit/8];