retry on transient wrapped httpi errors (#566)

* add httpclient timeout to backoff since it is the most preferred by httpi

* retry http client error subclasses since we use include? instead of is_a? on these

* retry on transient wrapped httpi errors too

lib/netsuite/utilities.rb

@@ -125,6 +125,8 @@ def backoff(options = {})
         exceptions_to_retry << OpenSSL::SSL::SSLErrorWaitReadable if defined?(OpenSSL::SSL::SSLErrorWaitReadable)
 
         # depends on the http library chosen
+        exceptions_to_retry << HTTPI::SSLError if defined?(HTTPI::SSLError)
+        exceptions_to_retry << HTTPI::TimeoutError if defined?(HTTPI::TimeoutError)
         exceptions_to_retry << HTTPClient::TimeoutError if defined?(HTTPClient::TimeoutError)
         exceptions_to_retry << HTTPClient::ConnectTimeoutError if defined?(HTTPClient::ConnectTimeoutError)
         exceptions_to_retry << HTTPClient::ReceiveTimeoutError if defined?(HTTPClient::ReceiveTimeoutError)