s3:winbindd: catch lookup_names/sids schannel errors over ncacn_ip_tcp (bug #7944)

s3:winbindd: catch lookup_names/sids schannel errors over ncacn_ip_tcp (bug #7944)

If winbindd connects to a domain controller it doesn't establish the lsa
connection over ncacn_ip_tcp direct. This happens only on demand.

If someone does a 'net rpc testjoin' and then a
wbinfo -n DOMAIN\\administrator, we'll get DCERPC faults with
ACCESS_DENIED/SEC_PKG_ERROR, because winbindd's in memory copy
of the schannel session key is invalidated.

This problem can also happen on other calls, but the
lookup_names/sids calls on thet lsa ncacn_ip_tcp connection
are the most important ones.

The long term fix is to store the schannel client state in a
tdb, but for now it's enough to catch the error and invalidate
the all connections to the dc and reestablish the schannel
session key.

The fix for bug 7568 (commit be396411a4e1f3a174f8a44b6c062d834135e70a)
made this worse, as it assumes winbindd's in memory session key is
always the current one.

metze