Thread safety, misc fixes, and refactoring (#51)

* Changing incorrect license in some source files.

* Changing CreateService to mimic CreateJob by setting the batch size to the instance count.

* Changing Getcerts to GetCerts to match the style of the rest of the codebase.

* Overhauled error handling. Backoff now recognizes temporary errors and continues to retry if it finds one.

* Changed thrift function call wrapper to be more explicitly named and to perform more safety checks.

* Moved Jitter function from realis to retry.

* API code is now more uniform and follows a certain template.

* Lock added whenever a thrift call is made or when a modification is done to the connection. Note that calling ReestablishConn externally may result in some race conditions. We will move to make this function private in the near future.

* Added test for Realis session thread safety. Tested ScheduleStatus monitor. Tested monitor timing out.

* Returning nil whenever there is an error return so that there are no ambiguities.

* Using defer with unlock so that the lock is still released if a panic is invoked.

response/response.go

@@ -17,9 +17,9 @@ package response
 
 import (
 	"bytes"
+	"errors"
 
 	"github.com/paypal/gorealis/gen-go/apache/aurora"
-	"github.com/pkg/errors"
 )
 
 // Get key from a response created by a StartJobUpdate call
@@ -39,6 +39,7 @@ func JobUpdateSummaries(resp *aurora.Response) []*aurora.JobUpdateSummary {
 	return resp.GetResult_().GetGetJobUpdateSummariesResult_().GetUpdateSummaries()
 }
 
+// Deprecated: Replaced by checks done inside of thriftCallHelper
 func ResponseCodeCheck(resp *aurora.Response) (*aurora.Response, error) {
 	if resp == nil {
 		return resp, errors.New("Response is nil")