Allow walkPayloadDeps visitor to control walk flow

Delegate the responsibility for determining whether the
walkPayloadDeps() should visit a child dependency to its do function.
This is needed to allow the visitor in checkApexAvailability() to avoid
checking the apex_available setting after crossing the APEX boundary.

Bug: 152878661
Test: m droid
Change-Id: If46a2f74b6eca670befc3aeae430650e85542346