incorrect handle of runinterval in agent/service/systemd.pp breaks catalog compilation

The runinterval parameter accepts values which match /^\d+[smhdy]?$/] pattern, so you can set 15m as value instead of 900.
But, when you set it to 15m as example you get a compilation error:

Error: Could not retrieve catalog from remote server: Error 500 on SERVER: Server Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, 'extlib::ip_to_cron' parameter 'runinterval' expects an Integer value, got String (file: /etc/puppetlabs/code/environments/dev/modules/puppet/manifests/agent/service/systemd.pp, line: 10, column: 14) on node puppetserver-003.puppetserver.local1.local.vagrant.dev.foo.com

This happens because runinterval is passed to extlibip_to_cron without making sure it is an integer.

I see this as a bug in puppet::agent::service::systemd class. The only workaround is to set runinterval to integer.

Start in manifests/agent/service/systemd.pp at line 10, where runinterval is passed to extlib::ip_to_cron. Reproduce catalog compilation with a value such as 15m and inspect the parameter handling. Done means the catalog compiles for the documented runinterval forms without breaking integer values.