pkg/aflow: add explicit DoWhile.MaxIterations #19163

Job	Run time
aux	3m 54s
build	3m 2s
race	9m 12s
race_dashboard	3m 7s
gvisor	3m 59s
dashboard	2m 45s
arch (presubmit_arch_freebsd)	6m 33s
old	7m 17s
arch (presubmit_arch_executor)	2m 53s
arch (presubmit_arch_netbsd)	3m 59s
arch (presubmit_arch_darwin)	3m 50s
arch (presubmit_arch_linux)	10m 39s
arch (presubmit_arch_windows)	3m 40s
arch (presubmit_arch_openbsd)	3m 49s
	1h 8m 39s

Provide feedback