Use memory cache in gss_acquire_cred_with_password

Use memory cache in gss_acquire_cred_with_password

gss_acquire_cred_with_password() was originally introduced in Solaris.
When we introduced it in 1.9, we unfortunately gave it different and
less useful semantics.  Restore this function to the Solaris
semantics, which are to always get credentials and store them in a
private memory ccache.  The caller can use gss_store_cred() to make
the resulting creds visible to other processes if desired.

ticket: 8152