Fix the default interface-interval docs and default value

Fix the default interface-interval docs and default value

When the interface-interval parser was changed from uint32 parser to
duration parser, the default value stayed at plain 60 which now means 60
seconds instead of 60 minutes.  Fix the default value and the
documentation to match the reality.

(cherry picked from commit de08c0088dbdeac7e97c343835f4fdb465dff27d)