script-snaplayers:  noop:  add comments
script-snaplayers:  noop:  update comments
layers.py:  'size' isn't really required except for LVM
util.py:  Fix logging to file

Detection of 'default' status was broken
util.py:  add 'timestr' property

Used in debug logs, whose timestamps are wrong or absent
libvirt and rbd layers:  operation retry fixes

Better debug output in libvirt attach/detach operations
- Show how many retries after initial failure

Wait for possible stalled watchers to be reaped in RBD clone removal
- Stalled watchers may take 30 seconds to timeout
- Add retry logic with debug messages