init: failed to set sys.usb.controller

With GKI we find in certain situations the timing of the drivers
loading is delayed as compared to a monolithic kernel.  This
introduces a race where during second stage init, the attributes
inside /sys/class/udc/ might not be set by the time
SetUsbController() is called.

To address this, we also call SetUsbController() until the property
sys.usb.controller is set at the bottom of the event loop.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 151950334
Test: make sure user space fastbootd comes up reliably for a GKI kernel
Change-Id: Iececd8ffa3e6641554d215d622d8dab72d85d34d