Revert "Add a wrapper class PartitionBuildProp"

Revert submission 1297095

Bug: 156131275
Reason for revert: Broken build
Reverted Changes:
I2fe7e93a2:Add a wrapper class PartitionBuildProp
Iac093a40d:Calculate the runtime fingerprint prefixes from bu...

Change-Id: Ie846d23b9f5c3325d021236725826512be7a3c78

tools/releasetools/build_image.py

@@ -509,9 +509,9 @@ def ImagePropFromGlobalDict(glob_dict, mount_point):
   d = {}
 
   if "build.prop" in glob_dict:
-    timestamp = glob_dict["build.prop"].GetProp("ro.build.date.utc")
-    if timestamp:
-      d["timestamp"] = timestamp
+    bp = glob_dict["build.prop"]
+    if "ro.build.date.utc" in bp:
+      d["timestamp"] = bp["ro.build.date.utc"]
 
   def copy_prop(src_p, dest_p):
     """Copy a property from the global dictionary.