Revert "O is API 26"

This reverts commit 8713882b.

Reason for revert:  b/37355569

Bug: 37480230
Bug: 37896931
Bug: 37355569
Change-Id: Ic07d948fd0b4a0a8434e1f4f0c8e559c4258cf5e

Android.mk

@@ -10,7 +10,7 @@ LOCAL_PATH:= $(call my-dir)
 # is made which breaks compatibility with the previous platform sepolicy version,
 # not just on every increase in PLATFORM_SDK_VERSION.  The minor version should
 # be reset to 0 on every bump of the PLATFORM_SDK_VERSION.
-sepolicy_major_vers := 26
+sepolicy_major_vers := 25
 sepolicy_minor_vers := 0
 
 ifneq ($(sepolicy_major_vers), $(PLATFORM_SDK_VERSION))