utils.sh: fetch_file: Use retry option for curl

Retry in case of failure a number of times (5 currently). With the provided
options it should use expontential backoff in case of failures, so should
cover most transient errors, while not spinning retries infinitely.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I66f9cf237897c406ac87f0371cb850e07c28a1dc
(cherry picked from commit 5fbd6bce417a476b156c859ef068617ef1be5eba)
diff --git a/utils.sh b/utils.sh
index 7acab04..0b15861 100644
--- a/utils.sh
+++ b/utils.sh
@@ -141,7 +141,7 @@
 		sa="${saveas+-o $saveas}"
 		echo "Fetch: $url -> $saveas"
 		# Use curl to support file protocol
-		curl --fail -sLS $sa "$url"
+		curl --fail --connect-timeout 5 --retry 5 -sLS $sa "$url"
 	else
 		sa="${saveas-.}"
 		echo "Fetch: $url -> $sa"