autotest: Consolidate WiFi/Bluetooth DNS name mangling

Adopt Bluetooth's style of rejecting IP addresses rather than
checking anything that doesn't look like the lab domain names.
Always prefer commandline specified hostnames to inferred hostnames.
While here, remove some WiFi test methods without callsites.

BUG=None
TEST=All of the following pass:
network_WiFi_SimpleConnect.wifi_checkWPA_TKIP (w/wo router_addr)
network_WiFi_AttenuatedPerf.ht40_c001
bluetooth_Sanity_Discovery

Change-Id: Ia76b0e159daeb6fe694dabd56a73fe544371de26
Reviewed-on: https://chromium-review.googlesource.com/236657
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
Tested-by: Christopher Wiley <wiley@chromium.org>
7 files changed