Relax the block count check on deallocation in env_test

It seems that on some FS we get more blocks than we ask for. This is already handled when checking the allocated number of blocks, but after the file is closed it checks for an exact number of blocks, which fails on my machine.

I changed the test to add one full page to the size, then calculate the expected number of blocks and check if the actual number of blocks is less or equal to that.
Ok, you edited the comment, so adding a new reply. If you round it to the nearest page up and then calculate the number of blocks from that, it will give the number as it does right now, so this does not work.

The size is 1048576 (1024*1024), which is exactly 256 pages. If you use that formular, you get 2048 blocks. The actual number of blocks I get on my machine is 2056.