(testsuite) Make diff_env() compatible with Solaris sed.

It appears to tolerate comments only at beginning of line.

test/lib/library.sh

@@ -16,10 +16,14 @@ add_comp_wordbreak_char() {
 # @param $3  Additional sed script
 diff_env() {
     diff "$1" "$2" | sed -e "
-	/^[0-9,]\{1,\}[acd]/d  # Remove diff line indicators
-	/---/d                 # Remove diff block separators
-	/[<>] _=/d             # Remove underscore variable
-	/[<>] PPID=/d          # Remove PPID bash variable
+# Remove diff line indicators
+        /^[0-9,]\{1,\}[acd]/d
+# Remove diff block separators
+        /---/d
+# Remove underscore variable
+        /[<>] _=/d
+# Remove PPID bash variable
+        /[<>] PPID=/d
         $3"
 } # diff_env()