Additional testing for v2 signer.
Additional testing for v2 signer.

In particular, test for additional query parameter (SecurityToken) for temporary credentials with a session.

calgaryscientific/aws-sdk-go,yxd-hde/aws-sdk-go,calgaryscientific/aws-sdk-go,tml/aws-sdk-go,rosenhouse/aws-sdk-go,xibz/aws-sdk-go,calgaryscientific/aws-sdk-go,wolfspyre/aws-sdk-go,zmarois/aws-sdk-go,radeksimko/aws-sdk-go,myshen/aws-sdk-go,wolfspyre/aws-sdk-go,xibz/aws-sdk-go,tml/aws-sdk-go,yxd-hde/aws-sdk-go,jasdel/aws-sdk-go,agworld/aws-sdk-go,zmarois/aws-sdk-go,radeksimko/aws-sdk-go,yxd-hde/aws-sdk-go,xibz/aws-sdk-go,myshen/aws-sdk-go,jjeffery/aws-sdk-go,zmarois/aws-sdk-go,radeksimko/aws-sdk-go,jjeffery/aws-sdk-go,zmarois/aws-sdk-go,jjeffery/aws-sdk-go,wolfspyre/aws-sdk-go,myshen/aws-sdk-go,radeksimko/aws-sdk-go,agworld/aws-sdk-go,aws/aws-sdk-go,rosenhouse/aws-sdk-go,tml/aws-sdk-go,rosenhouse/aws-sdk-go,agworld/aws-sdk-go,xibz/aws-sdk-go,yxd-hde/aws-sdk-go,calgaryscientific/aws-sdk-go,myshen/aws-sdk-go,agworld/aws-sdk-go