Remove accidentally duplicated RNDCExecutor code

This code has probably been accidentally added during some rebase. The
actual RNDCExecutor and related classes are in isctest/rndc.py. Remove
the duplicated and unused code from isctest/log.py, as it doesn't belong
there.

bin/tests/system/isctest/log.py

@@ -289,79 +289,3 @@ class WatchLogFromHere(WatchLog):
     def _seek_on_enter(self) -> None:
         if self._fd:
             self._fd.seek(0, os.SEEK_END)
-
-
-# pylint: disable=too-few-public-methods
-class RNDCExecutor(abc.ABC):
-    """
-    An interface which RNDC executors have to implement in order for the
-    `NamedInstance` class to be able to use them.
-    """
-
-    @overload
-    def call(self, ip: str, port: int, command: str, timeout: int = 10) -> str: ...
-
-    @overload
-    def call(
-        self, ip: str, port: int, command: List[str], timeout: int = 10
-    ) -> str: ...
-
-    @abc.abstractmethod
-    def call(
-        self, ip: str, port: int, command: Union[str, List[str]], timeout: int = 10
-    ) -> str:
-        """
-        Send RNDC `command` to the `named` instance at `ip:port` and return the
-        server's response.
-        """
-
-
-class RNDCException(Exception):
-    """
-    Raised by classes implementing the `RNDCExecutor` interface when sending an
-    RNDC command fails for any reason.
-    """
-
-
-class RNDCBinaryExecutor(RNDCExecutor):
-    """
-    An `RNDCExecutor` which sends RNDC commands to servers using the `rndc`
-    binary.
-    """
-
-    def __init__(self) -> None:
-        """
-        This class needs the `RNDC` environment variable to be set to the path
-        to the `rndc` binary to use.
-        """
-        rndc_path = os.environ.get("RNDC", "/bin/false")
-        rndc_conf = os.path.join("..", "_common", "rndc.conf")
-        self._base_cmdline = [rndc_path, "-c", rndc_conf]
-
-    @overload
-    def call(self, ip: str, port: int, command: str, timeout: int = 10) -> str: ...
-
-    @overload
-    def call(
-        self, ip: str, port: int, command: List[str], timeout: int = 10
-    ) -> str: ...
-
-    def call(
-        self, ip: str, port: int, command: Union[str, List[str]], timeout: int = 10
-    ) -> str:
-        """
-        Send RNDC `command` to the `named` instance at `ip:port` and return the
-        server's response.
-        """
-        cmdline = self._base_cmdline[:]
-        cmdline.extend(["-s", ip])
-        cmdline.extend(["-p", str(port)])
-        cmdline.extend(shlex.split(command) if isinstance(command, str) else command)
-
-        try:
-            return subprocess.check_output(
-                cmdline, stderr=subprocess.STDOUT, timeout=timeout, encoding="utf-8"
-            )
-        except subprocess.SubprocessError as exc:
-            msg = getattr(exc, "output", "RNDC exception occurred")
-            raise RNDCException(msg) from exc