Extract client behaviour outside the main #119

Job	Run time
build-macos (1.20.x, darwin, amd64)	32s
build-macos (1.20.x, darwin, arm64)	40s
build-linux (1.20.x, linux, ssh3-testuser, ssh3-testpasswd, /home/ssh3-testuser, amd64, gcc)	52s
build-macos (1.21.x, darwin, amd64)	40s
build-linux (1.21.x, linux, ssh3-testuser, ssh3-testpasswd, /home/ssh3-testuser, amd64, gcc)	1m 8s
build-other-unix (1.20.x, openbsd, amd64)	19s
build-macos (1.21.x, darwin, arm64)	20s
build-other-unix (1.20.x, openbsd, 386)	25s
build-other-unix (1.20.x, openbsd, arm64)	22s
build-other-unix (1.20.x, openbsd, arm)	20s
build-other-unix (1.20.x, freebsd, amd64)	22s
build-other-unix (1.20.x, freebsd, 386)	23s
build-other-unix (1.20.x, freebsd, arm64)	27s
build-other-unix (1.20.x, freebsd, arm)	21s
build-other-unix (1.20.x, linux, 386)	27s
build-other-unix (1.20.x, linux, arm)	24s
build-other-unix (1.21.x, openbsd, amd64)	19s
build-other-unix (1.21.x, openbsd, 386)	18s
build-other-unix (1.21.x, openbsd, arm64)	18s
build-other-unix (1.21.x, openbsd, arm)	22s
build-other-unix (1.21.x, freebsd, amd64)	24s
build-other-unix (1.21.x, freebsd, 386)	22s
build-other-unix (1.21.x, freebsd, arm64)	22s
build-other-unix (1.21.x, freebsd, arm)	26s
build-other-unix (1.21.x, linux, 386)	24s
build-other-unix (1.21.x, linux, arm)	26s
	11m 43s

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