test: Remove global wait_until from p2p_getdata #

Summary:

Using the global wait_until makes it impossible to adjust the timeout based on the hardware the test is running on.

Fix that by using the mininode member function.

This is a backport of Core PR19060

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D9164