Description of problem:

In 4.11, PolicyGen allows the user to override the ZTP predefined policy evaluation intervals. The ACM policy evaluation interval can be overridden in PGT (per template or per sourceFiles object). 

ACM accepts the string format of the Duration type. However, PolicyGen does not validate the values defined in PGT and it simply passes the user supplied value to ACM. PoliyGen should implement the same validation to prevent the user entering an invalid duration string

Version-Release number of selected component (if applicable): 4.11

How reproducible:

Steps to Reproduce:
1. Create a PGT with an invalid time duration string in  evaluationInterval fields
2. Run policygenerator binary with this PGT
3.  Expect an error

Actual results:

Expected results:

No error returned

Additional info: