ZFS: fix the delegate tests

These tests have never worked correctly

• Replace runwattr with sudo
• Fix a scoping bug with the "dtst" variable
• Cleanup user properties created during tests
• Eliminate the checks for refreservation and send support. They will always be supported.
• Fix verify_fs_snapshot. It seemed to assume that permissions would not yet be delegated, but that's not how it's actually used.
• Combine verify_fs_promote with verify_vol_promote
• Remove some useless sleeps
• Fix backwards condition in verify_vol_volsize
• Remove some redundant cleanup steps in the tests. cleanup.ksh will handle everything.
• Disable some parts of the tests that FreeBSD doesn't support:
  • Creating snapshots with mkdir
  • devices
  • shareisci
  • sharenfs
  • xattr
  • zoned

The sharenfs parts could probably be reenabled with more work to remove the
Solarisms.

MFC after: 2 weeks
Sponsored by: Axcient
Differential Revision: https://reviews.freebsd.org/D21898