Bug 16912: Koha::Patrons - Move AddEnrolmentFeeIfNeeded to ->add_enrolment_fee_if_needed

Bug 16912: Koha::Patrons - Move AddEnrolmentFeeIfNeeded to ->add_enrolment_fee_if_needed

This patch moves the code of the C4::Members::AddEnrolmentFeeIfNeeded
subroutine to the Koha::Patron->add_enrolment_fee_if_needed method.
The behavior should be unchanged.

Test plan:
1/ Define enrolment fee for 2 patron categories
2/ Create a patron using the first category
=> The patron should be charged
3/ Change the patron category to the other one
=> The patron should be charged again

Signed-off-by: Aleisha Amohia <aleishaamohia@hotmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>