Minor error fixes

Clear the error in pkt when we notice that the remote is starting to
send the packfile.

Fix the format string for Windows networking errors.

src/netops.c

@@ -35,7 +35,7 @@ static void net_set_error(const char *str)
 	size = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 			     0, error, 0, (LPSTR)&err_str, 0, 0);
 
-	giterr_set(GITERR_NET, "%s: $s", str, err_str);
+	giterr_set(GITERR_NET, "%s: %s", str, err_str);
 	LocalFree(err_str);
 }
 #else

src/pkt.c

@@ -217,6 +217,7 @@ int git_pkt_parse_line(
 		 * server is trying to send us the packfile already.
 		 */
 		if (bufflen >= 4 && !git__prefixcmp(line, "PACK")) {
+			giterr_clear();
 			*out = line;
 			return pack_pkt(head);
 		}