Fix argument type in MtpDatabase#getObjectPropertyValue.

In MTP code, we use jint for ID (e.g. object handle) and code (property
code). But getObjectPropertyValue takes jlong and it causes missing
property values in Java code. Previously we passed the long value to
Map<Integer, MtpPropertyGroup>#get(Integer) and the compiler somehow
accepted the code. However it actually takes Long at runtime, so the
properties are never found.

BUG=26437284
Change-Id: I79defd325ea5d20c4dce84d891d984e24abcacc5