System sound will turn to 0% after execute sound related test cases.

[Gabriel Zhi Chen]

Plainbox version: 0.22.1 and 0.22.2

Steps:
1. Install plainbox 0.22.1 or plainbox 0.22.2 on system.
2. Execute 'checkbox-cli'.
3. Select OME testplan, such as 'Sutton full test – 14.04'.
4. Adjust the volume to 100%.
5. Run then testplan and go to test case 'Audio/playback_auto'
6. Verify the volume in indicator.

Expected result:
The test case is pass and the volume is 100%

Actual result:
The test case is pass, but the volume is 0%

Notes:
Though the test case is pass, the volume is 0%. It will lead to the rest of audio test case failed after let the volume maintain the value '0%'. So if we wan to get the rest of audio test case 'PASS', we have to adjust volume value manually after execute every audio test case.

Further analyze:
-----------------------------------------------------------------
Adjust the volume to 100%, execute command '$ pactl list | less',
    Sink #0
     Volume: 0: 100% 1: 100%

After run test case 'Audio/playback_auto', '$ pactl list | less',
    Sink #0
     Volume: 0: 0% 1: 0%
-----------------------------------------------------------------
adjust the volume to 98%, execute command '$ pactl list | less',
    Sink #0
     Volume: 0: 98% 1: 98%

After run test case 'Audio/playback_auto', '$ pactl list | less',
    Sink #0
     Volume: 0: 8% 1: 8%
-----------------------------------------------------------------
Conclusion, after run a audio related test case, the value of Volume in 'Sink #0' get the prev-value's unit position, not the totally.

[Pierre Equoy (pieq)]

Confirmed with plainbox 0.22.2.

1. Set volume to 64%
2. run:
    plainbox run -i .*audio/playback_auto
3. Check volume
→ Volume is set to 4%

It looks like plainbox “truncates” the volume value and restores it with the bad value.

[Pierre Equoy (pieq)]

I found the root cause.

We use a script (in `checkbox-support/checkbox_support/scripts/audio_settings.py`) to store and restore the audio values before and after testing.

This script uses an erroneous regular expression that only returns one digit instead of several.

[Pierre Equoy (pieq)]

Patch made and tested OK.

Merge proposed here: https://code.launchpad.net/~pierre-equoy/checkbox/fix-1489817-audio-settings-volume-regexp/+merge/269838