1. Added AugustaOrGreater method to Helpers class (which is preferred method over MethodExists to check if a xapi call is available on a server). Also removed MethodExists method.
2. Utilized AugustaOrGreater method in GetDRMissingSRs method in both VM and VM_appliance classes.
1. Added MethodExists method to Helpers class: this method tests wheather given method exists already.
2. Utilized new Helpers method in VM and VM_appliance classes.
3. Fixed ACTION_MULTIPLE_DR_TASK_CREATE_ messages.
Signed-off-by: Adrian Jachacy <Adrian.Jachacy@citrix.com>