build: move some of hack/lib/ into a new cluster/lib/

Some functionality in hack/lib is currently depended on by
cluster/common.sh so kube-up from the full release tar (which
does not include hack/) is currently broken. With this PR we
create cluster/lib/ and move the necessary bits from hack/
over to get kube-up working again.

Fixes: 96d1b8d1b2
Signed-off-by: Mike Danese <mikedanese@google.com>

hack/lib/util.sh

@@ -176,17 +176,6 @@ kube::util::find-binary() {
   echo -n "${bin}"
 }
 
-# Wait for background jobs to finish. Return with
-# an error status if any of the jobs failed.
-kube::util::wait-for-jobs() {
-  local fail=0
-  local job
-  for job in $(jobs -p); do
-    wait "${job}" || fail=$((fail + 1))
-  done
-  return ${fail}
-}
-
 # Run all known doc generators (today gendocs, genman, and genbashcomp for kubectl)
 # $1 is the directory to put those generated documents
 kube::util::gen-docs() {