Fix is_timestamp_in_bounds 'now' default value
Fix is_timestamp_in_bounds 'now' default value

The `now` parameter to be able to spoof the current date when
unit-testing.  This parameter's default value is currently
`datetime.now()` which is evaluated when the method is instantiated then
never updated.

Fixes #39

Change-Id: I5a4f605093ca52018bb2310052de2e502fffdacd

enovance/dci-control-server,redhat-cip/dci-control-server,enovance/dci-control-server,redhat-cip/dci-control-server