Revert "avbtool: Avoid using $(ANDROID_VERITY_MODE) for now."

Boot loaders on both devices in question now support substituting
$(ANDROID_VERITY_MODE) to the correct value.

This reverts commit d3201be54d7e6a81e39fbdd4ef55b18289cc7c1c.

Bug: 38263429
Change-Id: I4099166bdbeeeb4ce298d99b1ac44ec876c907b9
Test: Manually tested on both devices.
diff --git a/avbtool b/avbtool
index db7c512..17b8a0d 100755
--- a/avbtool
+++ b/avbtool
@@ -2285,7 +2285,7 @@
     c += ' {}'.format(str(ht.salt).encode('hex'))  # salt
     if ht.fec_num_roots > 0:
       c += ' 10'  # number of optional args
-      c += ' restart_on_corruption'
+      c += ' $(ANDROID_VERITY_MODE)'
       c += ' ignore_zero_blocks'
       c += ' use_fec_from_device PARTUUID=$(ANDROID_SYSTEM_PARTUUID)'
       c += ' fec_roots {}'.format(ht.fec_num_roots)
@@ -2296,7 +2296,7 @@
       c += ' fec_start {}'.format(ht.fec_offset/ht.data_block_size)
     else:
       c += ' 2'  # number of optional args
-      c += ' restart_on_corruption'
+      c += ' $(ANDROID_VERITY_MODE)'
       c += ' ignore_zero_blocks'
     c += '" root=/dev/dm-0'