adb: Increase the max number of emulator instances to 64

When the ADB server starts, it probes the localhost ports to find
existing emulator instances, starting from 5555 with increments of
2, and stopping after ADB_LOCAL_TRANSPORT_MAX tries, which was
set to 16.

This means that the ADB server could not detect on startup more
than 16 existing emulator instances.

This increases the limit to 64, to match a corresponding change
on the emulator side.

  See https://android-review.googlesource.com/#/c/83553/

Change-Id: I35c69f8017298c3e5797bd396b8d788d44eaa00f