ApexManager: Allow blocking Binder calls

When ApexManager switched from using ServiceManager.getService to using Binder.waitForService to retrieve apexservice, it lost the call to Binder.allowBlocking that was inside getService. Since ApexManager currently makes several synchronous binder calls, this call is needed to avoid Log.wtf()s.

Bug: 153360345
Test: atest ApexManagerTest
Change-Id: I6016477b20754a6dc0f31588bae4e679f08a1ba2