QA output created by 290

### Test 'qemu-io -c discard' on a QCOW2 image without a backing file

# Create an image with compat=0.10 without a backing file
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
# Fill all clusters with data and then discard them
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Read the data from the discarded clusters
read 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Output of qemu-img map
Offset          Length          Mapped to       File
# Create an image with compat=1.1 without a backing file
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
# Fill all clusters with data and then discard them
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Read the data from the discarded clusters
read 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Output of qemu-img map
Offset          Length          Mapped to       File

### Test 'qemu-io -c discard' on a QCOW2 image with a backing file

# Create a backing image and fill it with data
Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=131072
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Create an image with compat=0.10 and a backing file
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base
# Fill all clusters with data and then discard them
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Read the data from the discarded clusters
read 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Output of qemu-img map
Offset          Length          Mapped to       File
0               0x20000         0x50000         TEST_DIR/t.qcow2
# Create an image with compat=1.1 and a backing file
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base
# Fill all clusters with data and then discard them
wrote 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Read the data from the discarded clusters
read 131072/131072 bytes at offset 0
128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
# Output of qemu-img map
Offset          Length          Mapped to       File
*** done