Changed requestname default value from nullptr to emptystring (#527)
Changed requestname default value from nullptr to emptystring (#527)

* Changed requestname default value from nullptr to emptystring

* Replaced nullptr with empty strings in the makerequest methods, as well as the attempt methods

* Comments for the change

* added error description to the comments

* Changed requestName description in comments and fixed typo

* comment aligment fix

cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,cedral/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,aws/aws-sdk-cpp,aws/aws-sdk-cpp,cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp,aws/aws-sdk-cpp,awslabs/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp