Reduce retries in gclient_utils

There are other retries (e.g. in git wrapper, gclient_scm) so we
shouldn't be retrying that much in gclient_utils.

In ideal case, we have a dedicated place where retries are determined,
and we make a retry decision based on stderr / exit code.

R=jojwang@google.com

Bug: 1359109
Change-Id: I97daa0d991a7294635e54b7a3d85a349c03c04c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3871979
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Joanna Wang <jojwang@chromium.org>

gclient_utils.py

@@ -39,8 +39,11 @@ else:
   import urllib.parse as urlparse
 
 
-RETRY_MAX = 3
-RETRY_INITIAL_SLEEP = 0.5
+# Git wrapper retries on a transient error, and some callees do retries too,
+# such as GitWrapper.update (doing clone). One retry attempt should be
+# sufficient to help with any transient errors at this level.
+RETRY_MAX = 1
+RETRY_INITIAL_SLEEP = 2  # in seconds
 START = datetime.datetime.now()