v2 authentication broken

[chatziko]

It seems to me that the removal of the lazy flags by a60f750 is causing has_temp_creds and has_SecurityToken to always return true in _sign_v2:

https://github.com/mrallen1/net-amazon-ec2/blob/ceeb817cc7c3606333cb4e0f7f454856583146fb/lib/Net/Amazon/EC2.pm#L296-L298

causing v2 authentication to fail.

No time to make a full showcase (sorry) but in my code I had to dirty-clean SecurityToken and temp_creds as a workaround.

delete $ec2->{SecurityToken};
delete $ec2->{temp_creds};