(PUP-11986) Add Amazon Linux package mapping

This commit adds a mapping for a package for Amazon Linux to use for the
systemd masked services test.

Author: mhashizume

acceptance/tests/resource/service/ticket_5024_systemd_enabling_masked_service.rb

@@ -17,6 +17,7 @@
 package_name = {'el'     => 'httpd',
                 'centos' => 'httpd',
                 'fedora' => 'httpd',
+                'amazon' => 'httpd',
                 'sles'   => 'apache2',
                 'debian' => 'cron', # apache2 does not create systemd service symlinks in Debian
                 'ubuntu' => 'cron', # See https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1447807