qemu-iotests: consider more cases in parsing qemu-io output

qemu-iotests: consider more cases in parsing qemu-io output

I got a bug report with test output diffs like this:

-4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+4 KiB, 1 ops; 0.0000 sec (inf EiB/sec and inf ops/sec)

This patch extends the regular expression to consider terabytes, petabytes and
exabytes, and to allow inf as value for the throughput.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>