Disable proxy-usage by unsetting the env-variable

Unset the environment-Variable https_proxy, as SOAP::Lite uses this internally
for https-requests.
Better errormessage when initial API-Call fails

When having wrong credentials (and maybe other wrong settings), the usage of
the test-API-Call in the return-statement led to the errormessage "No such file
or directory". Which is very misleading.

Separating the (useless) call to a separate line exits the process with a
proper errormessage.