Unset the http_proxy environment variable before running tests.
Unset the http_proxy environment variable before running tests.

Two connection tests (test_constructor and test_connection_to_unusual_port)
assume that there is no external real proxy in the test environment. Turns
out LibcloudConnection() will honor a http_proxy shell variable if it's set,
so if the test suite is run in such an environment, these tests will fail.

Signed-off-by: Quentin Pradet <d17611fde61d73f8de1b8b01bc47d446558ccd8e@apache.org>

ByteInternet/libcloud,Kami/libcloud,mistio/libcloud,andrewsomething/libcloud,andrewsomething/libcloud,apache/libcloud,Kami/libcloud,Scalr/libcloud,mistio/libcloud,apache/libcloud,ByteInternet/libcloud,Kami/libcloud,Scalr/libcloud,andrewsomething/libcloud,apache/libcloud,Scalr/libcloud,ByteInternet/libcloud,mistio/libcloud