datatop: fix file line count helper function always returns 0 lines

When porting the snapshot, a change was made to
dtop_get_file_line_amount() to initialize rc to -1. glibc defines
EoF as -1 thus causing the for loop to never get executed. A line count
of 0 was getting returnd thus causing ~1500 data points to not get
polled. Instead, initialize rc to 0.

Change-Id: I8e7a93f5efd535d662c13fa81cd5d0e421ad5a6b

datatop/src/datatop_fileops.c

@@ -153,7 +153,7 @@ void dtop_close_file(FILE *fw)
  */
 int dtop_get_file_line_amount(char *name)
 {
-	signed char rc = -1;
+	signed char rc = 0;
 	int line_count = 0;
 	FILE *file = fopen(name, "r");
 	while (rc != EOF) {