meta-google: gbmc-ncsi-config: Fix hostname parsing

This makes it more flexible and supports hostnames that have extra
hyphens.

Tested: Against a number of hostnames to verify correctness

ytbbg7-n18.prod.google.com
  ytbbg7
  prod.google.com
ytbbg7.prod.google.com
  ytbbg7
  prod.google.com
ytbbg7-n18.google.com
  ytbbg7
  google.com
ytbbg7.google.com
  ytbbg7
  google.com
ndn44-nfd01.corp.google.com
  ndn44
  corp.google.com
ndn44.corp.google.com
  ndn44
  corp.google.com
pnhuna-bf4-nfd01.prod.google.com
  pnhuna-bf4
  prod.google.com
pnhuna-bf4.prod.google.com
  pnhuna-bf4
  prod.google.com
ytbbg7-n18.prod.bhgoogle.com
ytbbg7.prod.bhgoogle.com
pnhuna-nzf0.prod.google.com
  pnhuna-nzf0
  prod.google.com

Change-Id: I4de218a4d77a34985d21098bf05db6ece990bb8f
Signed-off-by: William A. Kennington III <wak@google.com>