dashboard/app: fix admin checks for dev_appserver #18480

Job	Run time
build	4m 23s
arch (presubmit_arch_executor)	3m 15s
arch (presubmit_arch_windows)	3m 38s
gvisor	4m 3s
aux	3m 56s
old	7m 3s
arch (presubmit_arch_netbsd)	3m 53s
arch (presubmit_arch_openbsd)	3m 57s
arch (presubmit_arch_linux)	10m 47s
arch (presubmit_arch_darwin)	3m 50s
dashboard	2m 7s
race	8m 52s
race_dashboard	2m 52s
arch (presubmit_arch_freebsd)	6m 51s
	1h 9m 27s

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