Merge from Widevine repo of http://go/wvgerrit/135984
If the MediaDrm property string debugIgnoreKeyboxCount is set to 1,
then the keybox will be ignored on the next initialization. This will
force an OTA keybox reprovisioning.
Equivalently, a 1 may be written to the file
L1/debug_ignore_keybox_count.txt.
In order to test a failed reprovisioning step, a value of 2 may be
used.
Bug: 187646550
Change-Id: Ie7d34a8b355398855f4ec43dd95dd73c5907bdeb