ceph-perf: fix classic compare crash and crimson SeaStore

ceph-perf: fix classic compare crash and crimson SeaStore

Drop cpu_cycles_per_op from injected acceptable rules so CBT compare does
not TypeError on float(None) when perf is unavailable.
Use {workload} in the GitHub report paths so HTML does not strip tags into
"//". For crimson SeaStore without spare NVMes, attach sparse images via
losetup and pass /dev/loop* (vstart rejects plain .img). Wipe only device
contents; reattach detached loops when BACK-FILE is missing; tear down
images only at job end.

Signed-off-by: Kautilya Tripathi <kautilya.tripathi@ibm.com>