replmd: Move link conflict handling into separate function

replmd: Move link conflict handling into separate function

Link conflict handling is a corner-case. The logic in
replmd_process_linked_attribute() is already reasonably busy/complex.
Split out the handling of link conflicts into a separate function so
that it doesn't detract from the core replmd_process_linked_attribute()
logic too much.

This refactor should not alter functionality.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13055

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>