XML host import deletes discovered host groups

Steps to reproduce:

1. On a fresh system, add host Master, add a discovery rule of type trapper, add a host prototype to the rule (host with the name and host group as LLD macros):
   
2. Export Master host to an XML file.
3. Send the JSON to the discovery rule:

   {
       "request": "sender data",
       "data": [
           { "{#GOOD.HOSTNAME}": "good.host1", "{#GOOD.HOSTGROUP}": "good.hostgroup1" },
           { "{#GOOD.HOSTNAME}": "good.host2", "{#GOOD.HOSTGROUP}": "good.hostgroup2" }
       ]
   }
   

4. Observe that there are two hosts - good.host1 (belongs to group good.hostgroup1) and good.host2 (belongs to group good.hostgroup2).
5. Import previously exported Master host; leave all options default

Result:
Both discovered groups good.hostgroup1, good.hostgroup2 have gone while discovered hosts good.host1, good.host2 are still present

Expected:
If there are no changes to the discovery rules of the imported host then all discovered entities must stay untouched.