Fix NFS tests (#42894)

Author: weirongw23-msft

sdk/storage/azure-storage-file-share/tests/test_nfs.py

@@ -51,7 +51,7 @@ def _setup(self, storage_account_name: str):
                 pass
 
     def teardown_method(self):
-        if self.fsc:
+        if self.is_live and self.fsc:
             try:
                 self.fsc.delete_share(self.share_name)
             except:

sdk/storage/azure-storage-file-share/tests/test_nfs_async.py

@@ -58,7 +58,7 @@ async def _setup(self, storage_account_name: str):
                     pass
 
     def teardown_method(self):
-        if self.fsc:
+        if self.is_live and self.fsc:
             try:
                 fsc = ShareServiceClient(
                     account_url=self.account_url,