Bluetooth: Sleep instead of dying on EOF

When a device is restarted, the UART may go away before the
packetizer.  Print an error and sleep in case it isn't really
a restart.

Bug: 70855323
Test: Repeated restarts, check for Bluetooth tombstones
Change-Id: I2b4e677451e826d40dcc9d063d80dc0e17fc9aca