ZTS: clean up leftover ibackup_trunc files

zfs_receive_raw_incremental did not clean up ibackup_trunc.* files
left over from running the test.

Also changing the path of the ibackup files so they can be placed
in the correct directories when /var/tmp is not the temporary
directory.

Reviewed-by: Giuseppe Di Natale <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: bunder2015 <[email protected]>
Closes openzfs#7430

tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_raw_incremental.ksh

@@ -49,14 +49,15 @@ function cleanup
 		log_must zfs destroy -r $TESTPOOL/$TESTFS2
 
 	[[ -f $ibackup ]] && log_must rm -f $ibackup
+	[[ -f $ibackup_trunc ]] && log_must rm -f $ibackup_trunc
 }
 
 log_onexit cleanup
 
 log_assert "ZFS should receive streams from raw incremental sends"
 
-typeset ibackup="/var/tmp/ibackup.$$"
-typeset ibackup_trunc="/var/tmp/ibackup_trunc.$$"
+typeset ibackup="$TEST_BASE_DIR/ibackup.$$"
+typeset ibackup_trunc="$TEST_BASE_DIR/ibackup_trunc.$$"
 typeset passphrase="password"
 typeset passphrase2="password2"
 typeset snap1="$TESTPOOL/$TESTFS1@snap1"