On userdebug & eng builds, change the owner/group of SJTAG sysfs files
that need to be written to 'system', so that BetterBug is able to write
these files.
Bug: 204381544
Test: Ensure that the writable files in the following directories have
'system' as their owner & group:
/sys/devices/platform/sjtag_ap/interface/
/sys/devices/platform/sjtag_gsa/interface/
Signed-off-by: Peter Csaszar <pcsaszar@google.com>
Change-Id: I1fd61f702960a266bc8a2f84d1a1358ccefe3c9c