Don't replace original stacktrace when error happens parsing inline template

Helps with debugging errors in template

before

     Puppet::Error:
       Failed to parse inline template: `@32bit_packages' is not allowed as an instance variable name at /Users/csanchez/dev/maestrodev/puppet/android/spec/fixtures/modules/wget/manifests/fetch.pp:36 on node carlos-mbook-pro.home
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/functions/inline_template.rb:17:in `rescue in block (2 levels) in <top (required)>'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/functions/inline_template.rb:14:in `block (2 levels) in <top (required)>'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/functions/inline_template.rb:9:in `collect'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/functions/inline_template.rb:9:in `block in <top (required)>'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/functions.rb:144:in `block (2 levels) in newfunction'

after

     Puppet::Error:
       Failed to parse inline template: `@32bit_packages' is not allowed as an instance variable name at /Users/csanchez/dev/maestrodev/puppet/android/spec/fixtures/modules/wget/manifests/fetch.pp:36 on node carlos-mbook-pro.home
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/templatewrapper.rb:110:in `instance_variable_set'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/templatewrapper.rb:110:in `block (2 levels) in result'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/templatewrapper.rb:108:in `each'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/parser/templatewrapper.rb:108:in `block in result'
     # /Users/csanchez/.rvm/gems/ruby-1.9.3-p484/gems/puppet-3.4.1/lib/puppet/util.rb:166:in `benchmark'