Inject WebEnvironment into ODLAuthenticator

Inject WebEnvironment into ODLAuthenticator

With the rework done in AAA-225 we no longer inject SecurityManager into
static contexts nor the WebEnvironment into the external web server.
This leads to SecurityUtils.getSubject() not being able to allocate a
subject -- and hence not working at all.

Rather than relying on static contexts, make sure we talk to the
WebEnvironment we create and use its SecurityManager to create subjects.

JIRA: AAA-215
Change-Id: I8ccc4411e31ab6b392a4be8211621fd940516935
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>