s4-drepl: Make refreshed schema a global one

s4-drepl: Make refreshed schema a global one

We need to do this as dsdb_reference_schema() function
clears "use_global_schema" ldb flag.

Basically what is going to happen is that after dsdb_reference_schema()
global_schema pointer will continue to point at old schema cache,
while "dsdb_schema" for LDB will point at the working_schema.

After replication is done, we reset "dsdb_schema" for the ldb
with an updated Schema cache, but this leaves global_schema pointer
with its old value, which is not up to date.
So we need to call dsdb_make_schema_global() again so that global_schema
points to a valid Schema cache.