Appease older versions of bash

Older versions of bash need the extra quotes. Otherwise, the entire
version gets assigned to 'v,' after replacing spaces with
periods. (e.g. v="4 9"; p="".)

Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20170824183617.180441-1-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>