Fix sdk version for api24-specific libraries

SDK level for some api24 static libraries is still set
to "current". This means that using newer APIs in
these libraries would go undetected.

Changing to 24.
Test: try using API 25 in code under /api24, should fail

Change-Id: I8e48594427f3fd9a5a6d80090e79860f75e1b441
5 files changed