sam: fix small oversight in cmd_filter #671

Job	Run time
build (ubuntu-latest)	2m 27s
build (ubuntu-latest, --disable-curses)	3m 16s
build (ubuntu-latest, --disable-lua)	2m 13s
build (ubuntu-latest, --disable-tre)	2m 35s
build (ubuntu-latest, --disable-selinux)	2m 29s
build (ubuntu-latest, --disable-acl)	2m 27s
build (ubuntu-latest, --disable-help)	4m 27s
build (ubuntu-20.04)	2m 22s
build (ubuntu-20.04, --disable-curses)	2m 33s
build (ubuntu-20.04, --disable-lua)	2m 13s
build (ubuntu-20.04, --disable-tre)	2m 28s
build (ubuntu-20.04, --disable-selinux)	2m 25s
build (ubuntu-20.04, --disable-acl)	2m 24s
build (ubuntu-20.04, --disable-help)	2m 24s
	36m 43s

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