installd: Simplify Dalvik cache path creation

Installd computes Dalvik cache path for a dex file by concatenating
'/classes.dex' to the APKs absolute path and then replacing all '/'
characters with '@'. OTA preopt does the same, only in reverse order,
i.e by concatenating '@classes.dex' to altered absolute path.

This patch unifies the two approaches so as to keep only one string
constant.

Change-Id: I69bb6bca831f45c873a0eb8580cf8d4b011f3b09
diff --git a/cmds/installd/installd.cpp b/cmds/installd/installd.cpp
index 1583f86..d5c3ccd 100644
--- a/cmds/installd/installd.cpp
+++ b/cmds/installd/installd.cpp
@@ -151,12 +151,11 @@
         return false;
     }
 
-    sprintf(path,"%s%s/%s/%s%s",
+    sprintf(path,"%s%s/%s/%s",
             android_data_dir.path,
             DALVIK_CACHE,
             instruction_set,
-            src + 1, /* skip the leading / */
-            DALVIK_CACHE_POSTFIX);
+            src + 1 /* skip the leading / */);
 
     char* tmp =
             path +
@@ -171,6 +170,7 @@
         }
     }
 
+    strcat(path, DALVIK_CACHE_POSTFIX);
     return true;
 }