adb: bump the local socket backlog to the maximum.

The listen backlog seems to be more meaningful on Darwin than on Linux,
resulting in connections failing with ECONNRESET. Bump it up to the
maximum supported value to make this less likely. 128 pending
connections ought to be enough for anybody.

Bug: http://b/74616284
Test: python test_device.py
Change-Id: I5fe0205924188cf18ca1fc1204f923ab5523eeb2