Don't copy unitialized values of SuffixMatchTree

[rgacogne]

Short description

Entries that are not endNodes are basically place-holder and don't have a valid value, so we shouldn't attempt to copy the value when we duplicate a node, or the whole tree.
Among other possible issues it triggers the Undefined Behavior Sanitizer:

dnsname.hh:236:126: runtime error: load of value 165, which is not a valid value for type 'bool'

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)