Remove secontext.h, secontext.cpp, hash.h

cryptfs.cpp and MetadataCrypt.cpp can use android::vold::sFsckContext directly.
hash.h is unuseful.

Test: make
Change-Id: I7acdac97d6ed1c9b2a5dc367fcea8aa2942192e8
diff --git a/cryptfs.cpp b/cryptfs.cpp
index 7c33449..41931de 100644
--- a/cryptfs.cpp
+++ b/cryptfs.cpp
@@ -33,7 +33,6 @@
 #include "Utils.h"
 #include "VoldUtil.h"
 #include "VolumeManager.h"
-#include "secontext.h"
 
 #include <android-base/parseint.h>
 #include <android-base/properties.h>
@@ -1610,7 +1609,7 @@
          * fs_mgr_do_mount runs fsck. Use setexeccon to run trusted
          * partitions in the fsck domain.
          */
-        if (setexeccon(secontextFsck())) {
+        if (setexeccon(android::vold::sFsckContext)) {
             SLOGE("Failed to setexeccon");
             return -1;
         }