kex: Prefer sha2 over sha1
kex: Prefer sha2 over sha1

Signed-off-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>
(cherry picked from commit b0f22fde62c6db09493299830c650cbeee28cb0c)

mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/ssh