Allow fallback to default loader when encountering errors on network boot #922

Job	Run time
f41 x64 build compile_commands.json	2m 51s
f41 x64 build	2m 23s
f40 x64 build	2m 14s
f41 aa64 cross-build	2m 3s
f39 x64 build	1m 55s
f40 aa64 cross-build	1m 59s
centos9 x64 build	1m 6s
f41 arm cross-build	1m 59s
centos8 x64 build	1m 13s
f40 arm cross-build	2m 3s
f39 ia32 build	2m 7s
f39 arm cross-build	1m 55s
centos8 ia32 build	1m 18s
f41 x64 cross-build	2m 1s
f40 x64 cross-build	2m 6s
f39 x64 cross-build	2m 10s
f41 ia32 cross-build	2m 20s
f40 ia32 cross-build	1m 54s
f39 ia32 cross-build	1m 55s
	37m 32s

Provide feedback