Roll gsutil version to 4.15.

tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py

Index: tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py
diff --git a/tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py b/tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py
old mode 100755
new mode 100644
index 779dd97f13dce1d5f076118b66accb3e3666974c..b92c9f8a43898dd6081607ee52aba1581933b048
--- a/tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py
+++ b/tools/telemetry/third_party/gsutilz/third_party/apitools/apitools/base/py/util.py
@@ -126,20 +126,17 @@ def CalculateWaitForRetry(retry_attempt, max_wait=60):
 
     Args:
       retry_attempt: Retry attempt counter.
-      max_wait: Upper bound for wait time.
+      max_wait: Upper bound for wait time [seconds].
 
     Returns:
-      Amount of time to wait before retrying request.
+      Number of seconds to wait before retrying request.
 
     """
 
     wait_time = 2 ** retry_attempt
-    # randrange requires a nonzero interval, so we want to drop it if
-    # the range is too small for jitter.
-    if retry_attempt:
-        max_jitter = (2 ** retry_attempt) / 2
-        wait_time += random.randrange(-max_jitter, max_jitter)
-    return min(wait_time, max_wait)
+    max_jitter = wait_time / 4.0
+    wait_time += random.uniform(-max_jitter, max_jitter)
+    return max(1, min(wait_time, max_wait))
 
 
 def AcceptableMimeType(accept_patterns, mime_type):