Agent: Remove context manager from _authenticate()

Since the PowerShellExploiter's _authenticate() method returns the
client object, it doesn't make sense for it to be constructed in a
context manager.

monkey/infection_monkey/exploit/powershell.py

@@ -74,8 +74,7 @@ class PowerShellExploiter(HostExploiter):
 
     def _authenticate(self, username: Optional[str], password: Optional[str]) -> Client:
         (ssl, auth, encryption) = utils.get_powershell_client_params(password)
-
-        with Client(
+        client = Client(
             self.host.ip_addr,
             username=username,
             password=password,
@@ -83,9 +82,12 @@ class PowerShellExploiter(HostExploiter):
             ssl=ssl,
             auth=auth,
             encryption=encryption,
-        ) as client:
+            connection_timeout=3,
+        )
+
         # attempt to execute dir command to know if authentication was successful
         client.execute_cmd("dir")
+
         return client
 
     def _execute_monkey_agent_on_victim(self) -> bool: