adb: Fix backup fallback

 * Check for existence of binary first

Change-Id: I5c1884655ae031f51cb935221ae7870b016e259d
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_system_core into kitkat
Conditionally Revert "put back the unused virtuals in Vector<>"

These symbols are needed for MR2 camera.tegra and other blobs,
but they conflict with KK blobs so define it for devices that
need it by setting COMMON_GLOBAL_CFLAGS += -DNEEDS_VECTORIMPL_SYMBOLS

Change-Id: I59e66074526f013918a29c3afc10e52b9812778c
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_system_core into kitkat