tests: remove unused functions

As found by
  git -C tests/ grep ^function | grep -vFe '.lua:' -e '.zcp:' | while IFS=":$IFS" read -r _ _ fn _; do [ $(git -C tests/ grep -wF $fn | head -2 | wc -l) -eq 1 ] && echo $fn; done
after all rounds this comes out to, sorted:
  check_slog_state
  chgusr_exec
  cksum_files
  cleanup_pools
  compare_modes
  count_ACE
  dataset_set_defaultproperties
  ds_is_snapshot
  get_ACE
  get_group
  get_min
  get_mode
  get_owner
  get_rand_checksum
  get_rand_checksum_any
  get_rand_large_recsize
  get_rand_recsize
  get_user_group
  getitem
  indirect_vdev_mapping_size
  is_dilos
  log_noresult
  log_notinuse
  log_other
  log_timed_out
  log_uninitiated
  log_warning
  num_jobs_by_cpu
  plus_sign_check_l
  plus_sign_check_v
  record_cksum
  rwx_node
  seconds_mmp_waits_for_activity
  set_cur_usr
  setup_mirrors
  setup_raidzs
  showshares_smb
  zfs_zones_setup

This, of course, doesn't catch recursive ones, or ones that log with
their own function name as a prefix, but

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13259

tests/test-runner/include/logapi.shlib

@@ -26,7 +26,11 @@
 # Copyright (c) 2012, 2020 by Delphix. All rights reserved.
 #
 
-. ${STF_TOOLS}/include/stf.shlib
+STF_PASS=0
+STF_FAIL=1
+STF_UNRESOLVED=2
+STF_UNSUPPORTED=4
+STF_UNTESTED=5
 
 # Output an assertion
 #
@@ -372,15 +376,6 @@ function log_unresolved
 	_endlog $STF_UNRESOLVED "$@"
 }
 
-# Perform cleanup and exit $STF_NOTINUSE
-#
-# $@ - message text
-
-function log_notinuse
-{
-	_endlog $STF_NOTINUSE "$@"
-}
-
 # Perform cleanup and exit $STF_UNSUPPORTED
 #
 # $@ - message text
@@ -399,51 +394,6 @@ function log_untested
 	_endlog $STF_UNTESTED "$@"
 }
 
-# Perform cleanup and exit $STF_UNINITIATED
-#
-# $@ - message text
-
-function log_uninitiated
-{
-	_endlog $STF_UNINITIATED "$@"
-}
-
-# Perform cleanup and exit $STF_NORESULT
-#
-# $@ - message text
-
-function log_noresult
-{
-	_endlog $STF_NORESULT "$@"
-}
-
-# Perform cleanup and exit $STF_WARNING
-#
-# $@ - message text
-
-function log_warning
-{
-	_endlog $STF_WARNING "$@"
-}
-
-# Perform cleanup and exit $STF_TIMED_OUT
-#
-# $@ - message text
-
-function log_timed_out
-{
-	_endlog $STF_TIMED_OUT "$@"
-}
-
-# Perform cleanup and exit $STF_OTHER
-#
-# $@ - message text
-
-function log_other
-{
-	_endlog $STF_OTHER "$@"
-}
-
 function set_main_pid
 {
 	_MAINPID=$1