Microsoft Azure's infrastructure as a service (IaaS) offering allows the management of virtual machines through a so-called cloud layer. As such, accessing a virtual machine through the OS itself is not necessary when resetting an admin password.

Virtual machines in Azure normally have a small piece of software, called a VM agent, installed on them. The VM agent is installed at the OS level (usually automatically) and communicates with Azure. This allows out-of-band user control over the operating system without needing to touch the OS itself. 

Once the VM Agent is installed on a virtual machine, you can manage the local admin password without needing to interact directly with the OS. This can be accomplished via PowerShell, using the Set-AzureRmVMAccessExtension command.

By using the Set-AzureRmVMAccessExtension command, you can reset the password and reboot the virtual machine so that the change takes effect.