Infinity loop when assign static IPs

[kei-yamazaki]

In commit id 6f5a63a, Infinity loop occurs when reserve static IPs more then 256.

Following is an example.

$ cat template.yml
networks:
- name: cf1
  subnets:
  - static:
    - 10.0.0.2 - 10.0.1.254
jobs:
- name: foo
  templates:
  - name: bar
  instances: 1
  networks:
  - name: cf1
    static_ips: (( static_ips(0) ))

$ spruce -D merge template.yml
DEBUG> Processing file 'template.yml'
DEBUG> $.networks: not found upstream, adding it
DEBUG> $.jobs: not found upstream, adding it
DEBUG> parsing `(( static_ips(0) ))': looks like a (( static_ips ... )) operator
DEBUG>  arguments:
DEBUG>   #0: parsed as unquoted integer literal '0'
DEBUG>
DEBUG> patching up YAML by evaluating outstanding operators
DEBUG>
DEBUG> running (( static_ips ... )) operation at $.jobs.0.networks.0.static_ips
DEBUG>   determining what job context (( static_ips ... )) was called in
DEBUG>   got it.  $.jobs.0
DEBUG>
DEBUG>   extracting job name from $.jobs.0.name
DEBUG>   got it.  job is foo
DEBUG>
DEBUG>   determining how many instances of job foo there are
DEBUG>   got it.  there are 1 instances of foo
DEBUG>
DEBUG>   checking to see if the caller asked for enough static_ips to provision all job instances (need at least 1)
DEBUG>   looks good.  asking for 1 IPs for a job with 1 instances
DEBUG>
DEBUG>   determining the pool of static IPs from which to provision

# gone away!