[diag] Handle errors of `TransmitPacket()` #18

Job	Run time
expects	31m 27s
channel-manager-csl	3m 48s
packet-verification-1-1-on-1-4	11m 7s
packet-verification-low-power	9m 4s
thread-1-4-gcc-m32	12m 7s
thread-1-4-posix	9m 29s
thread-1-4-gcc-m64	11m 31s
thread-1-4-clang-m32	9m 59s
thread-1-4-clang-m64	9m 54s
upload-coverage	0s
	1h 48m 26s

Provide feedback