fix a (u|g)IDMappings type value convertion error #5554

Job	Run time
cross-i386	1m 38s
test (ubuntu-20.04, 1.20.x, rootless, -race)	6m 9s
cross-i386 (runc_nodmz)	1m 27s
test (ubuntu-20.04, 1.20.x, rootless)	6m 30s
test (ubuntu-20.04, 1.20.x, -race)	6m 45s
test (ubuntu-20.04, 1.20.x)	6m 15s
test (ubuntu-20.04, 1.21.x, rootless, -race)	6m 38s
test (ubuntu-20.04, 1.21.x, rootless)	5m 54s
test (ubuntu-20.04, 1.21.x, -race)	7m 4s
test (ubuntu-20.04, 1.21.x)	6m 14s
test (ubuntu-20.04, 1.21.x, criu-dev)	6m 45s
test (ubuntu-22.04, 1.20.x, rootless, -race)	9m 33s
test (ubuntu-22.04, 1.20.x, rootless, -race, runc_nodmz)	9m 30s
test (ubuntu-22.04, 1.20.x, rootless)	9m 0s
test (ubuntu-22.04, 1.20.x, rootless, runc_nodmz)	9m 15s
test (ubuntu-22.04, 1.20.x, -race)	7m 58s
test (ubuntu-22.04, 1.20.x, -race, runc_nodmz)	8m 2s
test (ubuntu-22.04, 1.20.x)	7m 6s
test (ubuntu-22.04, 1.20.x, runc_nodmz)	7m 33s
test (ubuntu-22.04, 1.21.x, rootless, -race)	9m 10s
test (ubuntu-22.04, 1.21.x, rootless, -race, runc_nodmz)	9m 17s
test (ubuntu-22.04, 1.21.x, rootless)	9m 35s
test (ubuntu-22.04, 1.21.x, rootless, runc_nodmz)	9m 10s
test (ubuntu-22.04, 1.21.x, -race)	7m 49s
test (ubuntu-22.04, 1.21.x, -race, runc_nodmz)	8m 15s
test (ubuntu-22.04, 1.21.x)	7m 13s
test (ubuntu-22.04, 1.21.x, runc_nodmz)	7m 9s
test (ubuntu-22.04, 1.21.x, criu-dev)	7m 45s
	3h 24m 39s

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