Failure to find an oem partition should not be a remount failure.

Many devices don't have an /oem partition, so find_mount should be
expected to fail, but shouldn't cause the overall remount to fail.

Also clean up all the error handling and reporting, and remove the
dead int* globals.

Bug: http://b/21024141
Change-Id: Ie31021b03c9cab8e972269d7d1ffe383cd30ee9e
(cherry picked from commit 9aa4fda4e64c1882faf019cc2a483ee4917e0c85)
diff --git a/adb/remount_service.h b/adb/remount_service.h
index e1763cf..7bda1be 100644
--- a/adb/remount_service.h
+++ b/adb/remount_service.h
@@ -19,7 +19,7 @@
 
 #include <string>
 
-int make_block_device_writable(const std::string&);
+bool make_block_device_writable(const std::string&);
 void remount_service(int, void*);
 
 #endif