[PATCH] ddraw/tests: Use winetest_push_context() in test_viewport().

[Marvin]

Hi,

While running your changed tests, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=113039

Your paranoid android.


=== w1064 (32 bit report) ===

ddraw:
ddraw7.c:18871: Test failed: Got unexpected color 0x0000ff00.

=== w1064_tsign (32 bit report) ===

ddraw:
ddraw7.c:18871: Test failed: Got unexpected color 0x00000040.

=== debian11 (32 bit Chinese:China report) ===

Report validation errors:
ddraw1: Timeout

=== debian11 (build log) ===

WineRunWineTest.pl:error: The task timed out

=== debian11 (64 bit WoW report) ===

Report validation errors:
ddraw7: Timeout

=== debian11 (build log) ===

WineRunWineTest.pl:error: The task timed out