common/dmlogwrites: genericize log writes target device

The dm-log-writes infrastructure is currently implemented to use
SCRATCH_DEV as a hardcoded data device. In preparation to allow use
of specialized devices in certain circumstances, genericize the code
to allow an arbitrary data device. This requires passing the target
device as a parameter to several helper functions from various
tests. No functional changes.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/generic/455

@@ -42,7 +42,7 @@ check_files()
 		local filename=$(basename $i)
 		local mark="${filename##*.}"
 		echo "checking $filename" >> $seqres.full
-		_log_writes_replay_log $filename
+		_log_writes_replay_log $filename $SCRATCH_DEV
 		_scratch_mount
 		local expected_md5=$(_md5_checksum $i)
 		local md5=$(_md5_checksum $SCRATCH_MNT/$name)
@@ -57,7 +57,7 @@ rm -rf $SANITY_DIR
 mkdir $SANITY_DIR
 
 # Create the log
-_log_writes_init
+_log_writes_init $SCRATCH_DEV
 
 _log_writes_mkfs >> $seqres.full 2>&1
 
@@ -92,7 +92,7 @@ _check_scratch_fs
 
 # check pre umount
 echo "checking pre umount" >> $seqres.full
-_log_writes_replay_log last
+_log_writes_replay_log last $SCRATCH_DEV
 _scratch_mount
 _scratch_unmount
 _check_scratch_fs
@@ -103,7 +103,7 @@ done
 
 # Check the end
 echo "checking post umount" >> $seqres.full
-_log_writes_replay_log end
+_log_writes_replay_log end $SCRATCH_DEV
 _scratch_mount
 for j in `seq 0 $((NUM_FILES-1))`; do
 	md5=$(_md5_checksum $SCRATCH_MNT/testfile$j)