fast-get: don't corrupt entries when failing #22943

Job	Run time
LP64-WIP	3m 59s
manifest-check	2m 56s
build-linux (mnfst, lnl)	4m 43s
build-linux (mnfst, wcl imx95)	7m 21s
build-linux (mnfst, ptl)	5m 58s
build-linux (mnfst, imx8m imx8ulp)	5m 19s
build-windows (mnfst, mtl)	8m 57s
build-windows (mnfst, ptl)	10m 32s
build-linux (-d, mnfst, lnl)	4m 48s
build-linux (mnfst, mtl)	4m 52s
build-windows (mnfst, imx8m imx8ulp)	9m 47s
build-windows (mnfst, imx8 imx8x)	11m 2s
build-windows (mnfst, lnl)	9m 32s
build-linux (mnfst, imx8 imx8x)	5m 2s
build-linux (mnfst, tgl-h)	4m 54s
build-windows (mnfst, tgl-h)	9m 23s
build-linux (mnfst, tgl)	4m 53s
build-windows (mnfst, tgl)	9m 37s
build-windows (-d, mnfst, lnl)	8m 59s
compare-linux-win	32s
	2h 13m 6s

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