ExecPlugins are broken when using KubeConfigs loaded from dict
**What happened (please include outputs or screenshots)**:

We use https://github.com/kubernetes-client/python/blob/master/kubernetes/base/config/kube_config.py#L820 to load Kubeconfigs from memory in Python, these Kubeconfigs have a configuration to use an Exec plugin to get an auth token (specifically we are trying to auth with an EKS cluster.)

https://github.com/kubernetes-client/python-base/pull/275/files#diff-a994e720c2c925ca342b251f2d057ab3a730a1bdc166e5766249a30bdf170a47R73 this PR to python-base attempts to pass the cwd of the config file to the exec plugin, however the cwd of a config file loaded from a dict is empty string (https://github.com/kubernetes-client/python/blob/master/kubernetes/base/config/kube_config.py#L542). When empty string is passed to subprocess.Popen, subprocess.Popen errors with "ERROR:root:[Errno 2] No such file or directory: ''" and does not run the auth plugin. 

Commenting out https://github.com/kubernetes-client/python-base/pull/275/files#diff-a994e720c2c925ca342b251f2d057ab3a730a1bdc166e5766249a30bdf170a47R73 fixed our auth issues completely, but the longterm fix is probably checking if the base_path is empty string and if so, pass None as the cwd to Popen. 

The issue means that anyone using EKS with load_kube_config_from_dict has been broken since this PR was merged. 

**What you expected to happen**:
Run the ExecProvider and return a token
**How to reproduce it (as minimally and precisely as possible)**:
Use load_kube_config_from_dict with an Authentication configuration using "command" for the user

**Anything else we need to know?**:

**Environment**:
- Kubernetes version (`kubectl version`):
- OS (e.g., MacOS 10.13.6):
Linux
- Python version (`python --version`)
3.8.10
- Python client version (`pip list | grep kubernetes`)
23.3.0
diff --git a/kubernetes/base/config/exec_provider.py b/kubernetes/base/config/exec_provider.py
index ef3fac661..08f0af2fb 100644
--- a/kubernetes/base/config/exec_provider.py
+++ b/kubernetes/base/config/exec_provider.py
@@ -53,7 +53,8 @@ class ExecProvider(object):
                 value = item['value']
                 additional_vars[name] = value
             self.env.update(additional_vars)
-        self.cwd = cwd
+        
+        self.cwd = cwd or None
 
     def run(self, previous_response=None):
         kubernetes_exec_info = {
['kubernetes/base/config/exec_provider.py']