add $password and $encryption_key parameters to VirtualMachine->reset_password

This is to match the API's parameters for this resource, to allow changing the current password and encryption key
fix undefined method error
Merge pull request #11 from james-lsn/3.1.0

Fix edge case when error returned is not an array
Merge pull request #12 from james-lsn/3.1.0-fix-reset-password

add $password and $encryption_key parameters to VirtualMachine->reset_password