ITS: add do_3a(do_af=False) to test_yuv_plus_raw.py

In test_yuv_plus_raw, do_capture use auto 3A mode,
So we need do 3A before capture.
In some platform such as qualcomm, 3A is not stable for
the first several frames in auto 3A mode.
So it's better to 3A before capture.

bug: 300037458
testing: OEM tested
Change-Id: I4e8637301a6598613c2a67bf2e90546514495fb7
Merged-In: I4e8637301a6598613c2a67bf2e90546514495fb7