(maint) Fix package acceptance test failure caused by gem provider changes.

The gem provider recently had the install_options feature implemented.
The provider was appending a nil value to the command arguments if there
are no install_options specified. This gets converted to an empty string
before the Kernel.exec call and causes gem to treat the empty string
as a gem name. The result is a failure when trying to install gems in
the acceptance test.

The fix is to append install_options only if specified on the resource.
(maint) Update gem provider spec for recent change.

The spec had an example which was expecting a nil
install_options by checking the 6th element in an array.
With the change to not append the install_options
unless specified, the example was passing but the
functionality no longer matched the example.

Changing the example to ensure 5 elements were
passed to execute instead of the previous 6.
Merge branch 'master' of https://github.com/puppetlabs/puppet