VMware: Fix return type of get_vnc_console()

Change I8f6a857b88659ee30b4aa1a25ac52d7e01156a68 changed the return type of
get_vnc_console(), but didn't update it in VMwareVCVMOps.

Closes-Bug: #1364849
Change-Id: I25edf0a19fa79439ed375ad128d0050718d04cb3
Merge "VMware: Fix return type of get_vnc_console()"