hashtable: Fix length calculation in hexport_r

The length returned by hexport_r has a few redundant characters.
This appears as NULL characters at the end so seems harmless.

Remove the surplus counts in two places

totlen += strlen(ep->key) + 2;
I'm guessing the +2 here is for = and sep char. But there is another
totlen += 2; line that does that.

size = totletn + 1;
Doesn't make sense and isn't justified with any comment.

Signed-off-by: Zubair Lutfullah Kakakhel <zubair@resin.io>

lib/hashtable.c

@@ -622,7 +622,7 @@ ssize_t hexport_r(struct hsearch_data *htab, const char sep, int flag,
 
 			list[n++] = ep;
 
-			totlen += strlen(ep->key) + 2;
+			totlen += strlen(ep->key);
 
 			if (sep == '\0') {
 				totlen += strlen(ep->data);
@@ -662,7 +662,7 @@ ssize_t hexport_r(struct hsearch_data *htab, const char sep, int flag,
 			return (-1);
 		}
 	} else {
-		size = totlen + 1;
+		size = totlen;
 	}
 
 	/* Check if the user provided a buffer */