hv_kvm.py: fix some lint issues introduced in 4b784cf8

In particular:

  - break as couple lines that were longer than 80 characters
  - fix a couple "comma not followed by a space"
  - fix an unused variable warning

Signed-off-by: Adeodato Simo <dato@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>