Multiple requests sent to HNAS can cause concurrency problems
and that ends up with 'SSC failed connection' errors. This
patch adds a retry decorator to _execute in HDS HNAS Manila
driver to fix this problem.
The current retry functionality in Manila always uses fixed
numbers to define the time to wait before performing the next
attempts. This behavior can make the retries of multiple
requests to collide in each attempt as they will wait the
same amount of time and try to use the same resource together
again. So additionally, this patch changes the behavior of
manila.utils.retry() to receive a parameter that allows the
function to implement randomly generated wait intervals.
Change-Id: Ib862f62517fcc8816781204b902119e9b20121e0
Closes-bug: 1491550
8dc3863e10