[storage] anvil-manage-storage-groups does not display correct information on Storage Group

```
# anvil-manage-storage-groups -vv --log-secure --show
Anvil Node: [an-anvil-01] - "Test Anvil! running on gravitar"
- Subnode: [an-a01n01] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [C3XOWR-RdWx-fhFQ-MKfl-KgNn-HFob-pj12zp]
- Subnode: [an-a01n02] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [gdevUa-kkAe-C58e-i1ra-mOBU-baK4-afuYA7]
- Storage group: [Node an-anvil-01, SG 1], UUID: [b834b40a-e5ab-492a-8903-633e6234a9bb]
- [an-a01n01]:[anvil-test-vg]
- [an-a01n02]:[anvil-test-vg]

# anvil-manage-storage-groups -vv --log-secure --anvil an-anvil-01 --group "$storageuuid" --add --member "$localvguuid"
Added the volume group: [anvil-test-vg] on the host: [ci] to the storage group: [Node an-anvil-01, SG 1]. The new member UUID is: [6c3546c7-b886-4e4b-ae96-673e3cd026ec].

# anvil-manage-storage-groups -vv --log-secure --show
Anvil Node: [an-anvil-01] - "Test Anvil! running on gravitar"
- Subnode: [an-a01n01] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [C3XOWR-RdWx-fhFQ-MKfl-KgNn-HFob-pj12zp]
- Subnode: [an-a01n02] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [gdevUa-kkAe-C58e-i1ra-mOBU-baK4-afuYA7]
- Storage group: [Node an-anvil-01, SG 1], UUID: [b834b40a-e5ab-492a-8903-633e6234a9bb]
- [an-a01n01]:[anvil-test-vg]
- [an-a01n02]:[anvil-test-vg]
- [ci]:[anvil-test-vg]

^^ so far so good

# anvil-manage-storage-groups -vv --log-secure --anvil an-anvil-01 --group "$storageuuid" --add --member "$localvguuid"
The volume group: [anvil-test-vg] on the host: [ci] is already a member of the storage group: [Node an-anvil-01, SG 1]. Nothing to do.

^^ perfect.

# anvil-manage-storage-groups -vv --log-secure --anvil an-anvil-01 --group "$storageuuid" --remove --member "$localvguuid"
Added the volume group: [anvil-test-vg] on the host: [ci] has been removed from storage group: [Node an-anvil-01, SG 1].

^^ "Added" should be "Removed" (minor details)

# anvil-manage-storage-groups -vv --log-secure --show
Anvil Node: [an-anvil-01] - "Test Anvil! running on gravitar"
- Subnode: [an-a01n01] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [C3XOWR-RdWx-fhFQ-MKfl-KgNn-HFob-pj12zp]
- Subnode: [an-a01n02] volume groups;
- [anvil-test-vg], size: [200.00 GiB], free: [190.00 GiB], internal UUID: [gdevUa-kkAe-C58e-i1ra-mOBU-baK4-afuYA7]
- Storage group: [Node an-anvil-01, SG 1], UUID: [b834b40a-e5ab-492a-8903-633e6234a9bb]
- [an-a01n01]:[anvil-test-vg]
- [an-a01n02]:[anvil-test-vg]
- [ci]:[anvil-test-vg]

^^ still there in the output, even if it´s no longer configured.

# anvil-manage-storage-groups -vv --log-secure --anvil an-anvil-01 --group "$storageuuid" --add --member "$localvguuid"
Added the volume group: [anvil-test-vg] on the host: [ci] to the storage group: [Node an-anvil-01, SG 1]. The new member UUID is: [6c3546c7-b886-4e4b-ae96-673e3cd026ec].
```