blktests: use patient module remover

This rebases the patient module remover series onto the current blktests tree and addresses all the feedback from v3 from a long time ago [0]. This came up recently as Swarna noticed the same flaky bug and I got reminded to re-send a new iteraiton.

We now have the modprobe --wait upstream so use that if avaiable.

The patient module remover addresses race conditions where module removal can fail due to userspace temporarily bumping the refcount (e.g., via blkdev_open() calls). If your version of kmod supports modprobe --wait, we use that. Otherwise we implement our own patient module remover.

[0] https://lore.kernel.org/all/[email protected]/T/#u

Changes in v4:
- Rebased onto current blktests master
- Fixed built-in module handling: _patient_rmmod() now checks for the existence of /sys/module/$module_sys/refcnt to detect built-in modules and returns success early (Shinichiro Kawasaki)
- Fixed timeout parameter timing issue: MODPROBE_PATIENT_RM_TIMEOUT_SECONDS is now evaluated dynamically inside _patient_rmmod() rather than at source time, allowing tests to override the timeout value (Shinichiro Kawasaki)
- Preserved SKIP_REASONS logic in _init_null_blk() when modprobe fails, so tests requiring loadable modules are properly skipped rather than failing (Shinichiro Kawasaki)
- Fixed typo in comment: "modprobe -p" -> "modprobe --wait" (Luis Chamberlain)
- Fixed path reference bug: used $module_sys instead of $module for /sys/module path checks (Luis Chamberlain)
- Combined nested while conditions for cleaner code style (Shinichiro Kawasaki)
- Removed redundant $module printing in error messages (Shinichiro Kawasaki)
- Updated to use --wait=TIMEOUT_MSEC syntax (with =) to match the upstream kmod implementation

Luis Chamberlain (2):
blktests: replace module removal with patient module removal tests/srp/rc: replace module removal with patient module removal

 common/multipath-over-rdma |  11 +---
 common/null_blk            |   6 +-
 common/nvme                |   9 +--
 common/rc                  | 126 +++++++++++++++++++++++++++++++++++++
 common/scsi_debug          |  14 ++---
 tests/srp/rc               |  19 ++----
 6 files changed, 148 insertions(+), 37 deletions(-)

2.51.0