[BUG] Fallback to extract pipelines from proc causes green failure in SOF test  #913

Describe the bug
On the PR test on CML_RVP_SDW_ZEPHYR, the SOF card disappeared in the middle due to unknown issue. If SOF card is not detected from the system, sof-test will try to extract pipelines from /proc, which usually are pipelines from USB sound card/Nvidia graphic card.
This causes green failures in SOF test.

For example, the passed case check-playback-10sec.sh actually tests USB sound card.

https://sof-ci.01.org/linuxpr/PR3642/build146/devicetest/
https://sof-ci.01.org/linuxpr/PR3645/build155/devicetest

Expected behavior
Fallback behavior should be under control, we should have an option to enable/disable Fallback mode, because we also use sof-test to test legacy HDA.