[wifi_test_utils] Fix for cnss diag

1. ag/12424554 broke Fuschia team's tests as the check for cnss_diag_file
was added to WifiBaseTest. It is moved to setup_class of WifiSoftApAcsTest.
2. Since cnss diag is supported only on pixel devices, utils methods are
updated to check if the device supports pixel logger before starting
cnss_diag log collection.

Bug: 160029496
Fixes: 160029496
Test: Verified the changes locally
Change-Id: I8bdd6664c46c4062d4577b086f5c5abbcace75f7
2 files changed
tree: a326664a1f5b41966792a55c17851631ae34234f
  1. acts/
  2. acts_tests/
  3. tools/
  4. wts-acts/
  5. Android.mk
  6. OWNERS
  7. PREUPLOAD.cfg