Duplicate declaration: Package[git] with ensure_packages

[philipfreude]

Using ensure_packages('git') for puppetmaster setup creates a duplicate declaration error when the package 'git' is included in another module with something else than ensure_packages('git') or ensure => present.

A good explanation can be found in this issue for another module:
willdurand/puppet-composer#44

I propose changing the

ensure_packages('git')

to a

if !defined(Package['git']) {
      ensure_packages('git')
}

which will solve the issue.

[philipfreude]

see #30

[fraenki]

Fix will be available in the upcoming 2.1.0.