Fixed issue 3390 and GSSAPI warnings

This forces winrm and thus gssapi gem to load immediately. This keeps Vagrant from crashing on some systems with a "Trace/BPT trap: 5" error. This fixes issue #3390.

This also suppresses the warnings emitted while the gssapi gem binds to the gssapi lib on the system, addressing issue #3258 and #3123.

WARNING: Could not load IOV methods. Check your GSSAPI C library for an update
WARNING: Could not load AEAD methods. Check your GSSAPI C library for an update