test/compress: clarify out-of-space error messages
test/compress: clarify out-of-space error messages

Use ERR rather than INFO to warn that it's a negative test else
the errors are seen but the warning to expect them isn't.
Also add comment to make it easier to follow code.

Signed-off-by: Fiona Trahe <7ba562cc372916cd557d0be347608f8b4da4f746@intel.com>
Acked-by: Adam Dybkowski <b636839fd6da8c90d3d28fcb76555ed5d2c5a673@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk