Fix gssapi credential handling.
Fix gssapi credential handling.

- Properly acquire and inquitre credentials to get the list of available
credentials.
- Avoid enforcing a specific username it breaks some use cases (k5login).
- Remove confusing references to delegated credentials as there is no code
that actually uses delegated credentials in the initialization case.

Signed-off-by: Siom Sorce <65f99581a93cf30dafc32b5c178edc6b0294a07f@redhat.com>
Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

robxu9/libssh,taikoo/libssh,elastichosts/libssh,Distrotech/libssh,kedazo/libssh,nviennot/libssh,mwgoldsmith/ssh,elastichosts/libssh,mwgoldsmith/libssh,kedazo/libssh,sebadoom/libssh,taikoo/libssh,wangshawn/libssh,sebadoom/libssh,Distrotech/libssh,mwgoldsmith/libssh,robxu9/libssh,wangshawn/libssh,robxu9/libssh,pouete/libssh,DouglasHeriot/libssh,robxu9/libssh,wangshawn/libssh,kedazo/libssh,nviennot/libssh,Distrotech/libssh,pouete/libssh,mwgoldsmith/libssh,mwgoldsmith/ssh,nviennot/libssh,wangshawn/libssh,elastichosts/libssh,DouglasHeriot/libssh,taikoo/libssh,nviennot/libssh,kedazo/libssh,sebadoom/libssh,mwgoldsmith/libssh,mwgoldsmith/ssh,Distrotech/libssh,mwgoldsmith/ssh,DouglasHeriot/libssh,sebadoom/libssh,pouete/libssh,DouglasHeriot/libssh,taikoo/libssh,pouete/libssh