Server operations don't work when the Nexus CR is in a different namespace

[LCaparelli]

Describe the bug

Server operations don't work when the Nexus CR is in a different namespace and fail due to a name resolution failure:

╰─ kubectl -n nexus-demo describe nexus
(...)
  Nexus Status:              Failure
  Reason:                    Failed to deploy Nexus: Get "http://nexus3:8081/service/rest/beta/security/users?userId=nexus-operator": dial tcp: lookup nexus3 on 10.96.0.10:53: no such host

To Reproduce
Steps to reproduce the behavior:

1. Install via OLM following the steps in Operator Hub
2. Create a separate namespace:

$ kubectl create namespace nexus-test`

3. Install a CR in that namespace:

$ echo "apiVersion: apps.m88i.io/v1alpha1
kind: Nexus
metadata:
  name: nexus3
spec:
  replicas: 1
  persistence:
    persistent: true
  useRedHatImage: false" | kubectl -n nexus-test apply -f -

4. Check the Nexus CR status

Expected behavior
The server operations succeed even if the operator is in another namespace.

Environment

╰─ kubectl version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.2", GitCommit:"52c56ce7a8272c798dbc29846288d7cd9fbae032", GitTreeState:"clean", BuildDate:"2020-04-16T11:56:40Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.0", GitCommit:"e19964183377d0ec2052d1f1fa930c4d7575bd50", GitTreeState:"clean", BuildDate:"2020-08-26T14:23:04Z", GoVersion:"go1.15", Compiler:"gc", Platform:"linux/amd64"}

Additional context
N/A

[LCaparelli]

Better wait for #161 so this can be properly tested