The mode in which to attach this disk, either READ_WRITE or
READ_ONLY. If not specified, the default is to attach the disk in
READ_WRITE mode.
Values:
UNDEFINED_MODE (0):
A value indicating that the enum field is not
set.
READ_ONLY (91950261):
Attaches this disk in read-only mode. Multiple VM instances
can use a disk in READ_ONLY mode at a time.
READ_WRITE (173607894):
[Default] Attaches this disk in READ_WRITE mode. Only one
VM instance at a time can be attached to a disk in
READ_WRITE mode.
