esx: Explicitly disable unused floppy devices

floppy0.present defaults to true. Therefore, it needs to be
explicitly set to false when the XML config doesn't specify the
corresponding floppy device.

Also update tests accordingly.

tests/xml2vmxdata/xml2vmx-parallel-device.vmx

@@ -5,6 +5,8 @@ uuid.bios = "56 4d 9b ef ac d9 b4 e0-c8 f0 ae a8 b9 10 35 15"
 displayName = "parallel-device"
 memsize = "4"
 numvcpus = "1"
+floppy0.present = "false"
+floppy1.present = "false"
 parallel0.present = "true"
 parallel0.fileType = "device"
 parallel0.fileName = "/dev/parallel0"