adb: add a way to make the server intentionally leak.

Add a way to test LeakSanitizer with the server by adding an
environment variable that intentionally leaks.

Test: ASAN_OPTIONS=detect_leaks=1:leak_check_at_exit=1 ADB_LEAK=1 adb server nodaemon
Change-Id: I7255d45335fa009dc9e5de99dff67af52bd70e06
1 file changed