Graph Template Cache is nullified too often when Graph Automation is running

[TheWitness]

Describe the bug

When graph automation is running and potentially thousands of graphs are created over a period of potentially hours, the Graph Template cache is cleared continually and leading to longer load times for the Graphs page.

To Reproduce

Steps to reproduce the behavior:

1. Run and automation process as described above

2. Add instrumentation to lib/auth.php to see that the cache is continually cleared

3. Check the Cacti log when rendering Graphs pages

Expected behavior

The cache should be more persistent.