autotest: Tolerate missing dhcpd on client systems.

While routers have to have dhcpd, client systems may not.  However,
WiFiClient uses LinuxSystem to look up its own capabilities.  Tolerate
that we may not have dhcpd in that case.

TEST=test_that --fast chromeos3-grover-host2 e:.*check11b passes.
BUG=chromium:294856

Change-Id: I7d0a9ef9371c4d28e39b13f2ded1f6e03277e12b
Reviewed-on: https://chromium-review.googlesource.com/170021
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
2 files changed