[REF] simplify retrieval of existing membership on membership renewal form

[eileenmcnaughton]

Overview

Minor code simplification on membership renewal form

Before

$currentMembership = CRM_Member_BAO_Membership::getContactMembership($contactID, $membershipTypeID,
      $is_test, $membershipID, TRUE
    );

getContactMembership is hard to read

After

$currentMembership = civicrm_api3('Membership', 'getsingle', ['id' => $membershipID]);

Technical Details

After stepping through the code I determined that if membershipID is passed into getContactMembership then it either

1. returns the membership id much like membership.get but with is_current_member calculated or
2. returns the owner membership in a similar format

However, the renewal form is not visible for a non-owner membership so getting the owner membership is cruft
from another form & only 1 applies. Calling the api is much more transparent

Comments

Cover in MembershipRenewalTest

[civibot]

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[colemanw]

Change makes sense to me.