Support Azure in test_check_virtwhat

[yuxisun1217]

In Azure ARM VM the CPU is not Microsoft:

Vendor ID:                ARM
  BIOS Vendor ID:         Ampere(R)
  Model name:             Neoverse-N1
    BIOS Model name:      Ampere(R) Altra(R) Processor

So use is_azure() to detect the Azure platform.

[liangxiao1]

LGTM, thanks @yuxisun1217