fix an icc warning on eng32

git-svn-id: file:///svn/toku/tokudb@7758 c7de825b-a66e-492c-adef-691d508d4ae1

db-benchmark-test/db-benchmark-test.c

@@ -167,7 +167,7 @@ static void fill_array (unsigned char *data, int size) {
     if (compressibility>0) {
 	int i;
 	for (i=0; i<size/compressibility; i++) {
-	    data[i] = random();
+	    data[i] = (unsigned char)random();
 	}
     }
 }