Publishing an SD file containing a geoprocessing service fails in a disconnected environment

**Describe the bug**
We have created a custom print service. When using the ArcGIS Python API 2.1 to publish this to an ArcGIS Server **in a disconnect / offline environment**, we first get a warning:
_Using Connection object over GIS object_

then directly the error:
_A connection error has occured: HTTPSConnectionPool(host='www.arcgis.com', port=443): Max retries exceeded with url: /sharing/rest/portals/self (Caused by NewConnectionError)_

**The problem is the new GIS-object being created in arcgis/geoprocessing/_support.py on line 378 to 384, where the Python API creates a new GIS object with no URL specified, which means it will try to reach out to www.arcgis.com per default.**

**To Reproduce**
Steps to reproduce the behavior:
Create an SD-file for a print service (probably other GP Services will fail as well)
```python
from arcgis.gis import GIS
gis = GIS("https://myportal.com/portal", "user", "pass")

sd_file = r"C:\temp\prinservice.sd"
# Get the first federated server
target_server = gis.admin.servers.list()[0]

target_server.publish_sd(sd_file)
```
error:
```python
A connection error has occured: HTTPSConnectionPool(host='www.arcgis.com', port=443): Max retries exceeded with url: /sharing/rest/portals/self (Caused by NewConnectionError)
```
**Screenshots**
If applicable, add screenshots to help explain your problem.

**Expected behavior**
A clear and concise description of what you expected to happen.

**Platform (please complete the following information):**
- OS: Windows Server 2022
- Python API Version 2.1

**Additional context**
The problem is the new GIS-object being created in arcgis/geoprocessing/_support.py on line 378 to 384, where the Python API creates a new GIS object with no URL specified, which means it will try to reach out to www.arcgis.com per default.

Problematic code, which can be worked around by commenting out the following (might cause other stuff to break?):
```python
if isinstance(gis, Connection):
log = logging.getLogger()
log.warning("Using Connection object over GIS object")
ngis = GIS(set_active=False)
ngis._con = gis
gis = ngis
```

Start with arcgis/geoprocessing/_support.py lines 378-384 and reproduce the failure using GIS, the first federated server, and publish_sd() in the issue. Trace how the GIS object is created when given a Connection, then verify that publishing an SD file to the disconnected portal no longer attempts to reach www.arcgis.com.

Written by the indexing model from the issue text.