Allow ExponentialRetryPolicy to be fully configured from the hadoop
configuration. Properties are already defined for this, so ensure that
they are passed along when the retry policy is constructed and that
documentation has been updated.

* Add spotbugs exclusion for IS2_INCONSISTENT_SYNC on
  NativeAzureFsInputStream.in to fix errant bug trigger introduced in
  PR apache#3149.
* Refactor TestExponentialRetryPolicy to use a variable with the value
  offset rather than hard-coded numbers in order to satisfy checkstyle.

…retry-policy

* Update doc formatting as requested to include backticks on class name
* Fix some spelling errors in testing_azure.md
* Add assertion failure messages for new test case