Fix 'domain\user' reporting in mremote

MSP-11053

#### Verification
 - [x] install mremote on a windows box
 - [x] store an rdp connection
 - [x] get a meterp session on that box
 - [x] `run post/windows/gather/credentials/mremote`
 - [x] *VERIFY*: creds created with proper domain storage for RDP connections instead of a user like "domain\\user"