Don't replace the https handler in the poolmanager

In order to keep the support for `--ssl-nocompression` it was decided to
overwrite the https HTTPAdapter in `requests` poolmanager. Although this
seemed to work correctly, it was causing some issues when using
glanceclient from other services that rely on requests and that were
also configured to use TLS.

THis patch changes implements a different strategy by using
`glance+https` as the scheme to use when `no-compression` is requested.

Closes-bug: #1350251
Closes-bug: #1347150
Closes-bug: #1362766

Change-Id: Ib25237ba821ee20a561a163b79402d1375ebed0b
Merge "Don't replace the https handler in the poolmanager"