Fix parallel h5diff option of tool location

tools/test/h5diff/testh5diff.sh.in

@@ -389,8 +389,8 @@ while [ $# -gt 0 ]; do
     case "$1" in
     -p)	# reset the tool name and bin to run ph5diff tests
 	TESTNAME=ph5diff
-	H5DIFF=ph5diff               # The tool name
-	H5DIFF_BIN=`pwd`/$H5DIFF
+	H5DIFF=../../src/h5diff/ph5diff  # The tool name
+	H5DIFF_BIN=`pwd`/$H5DIFF    # The path of the tool binary
 	pmode=yes
 	shift
 	;;