block: close the remaining iotests exclusions #114

xtask/ruvm-iotests-expected.toml lists the iotests that pass against QEMU 11.1 but not against ruvm. M3 closed with each of them explained, but every entry is a real gap and should go away over time.

• qemu-io runs aio requests one at a time, so writes held at a blkdebug breakpoint do not interleave: 046, 060, 271, and 077 for raw and nbd
• No quorum driver: 110, 312, 081, 148
• qemu-io -s (snapshot=on): 052 for qcow2 and raw
• Build with zstd compression for qcow2: 287, 303
• qemu-nbd -B does not find persistent bitmaps: 223, qemu-img-bitmaps
• A writable NBD export on an inactive node is refused: qsd-migrate for qcow2 and raw
• 071: blkverify reports a mismatch where QEMU's reads agree
• 074: stdout and stderr ordering, Rust line buffers stdout where C fully buffers a pipe
• 244: lock conflict on an external data file
• qemu-img-close-errors: a bitmap write failure on close is ignored and commit exits 0
• qsd-jobs: quitting does not cancel a running job
• nbd 241: an unaligned image is advertised with minimum block 1

280, 286 and 205 also failed once while the test box was overloaded and passed when run alone, so they may need a look if they show up again.