Re-transmitting storage transmitter might cause invalid URL

[jondequinor]

Describe the bug

To my eyes, if I call _transmit_numerical_record or _transmit_blob_record multiple times (maybe due to networking errors or whatever), you might append f"{self._uri}?realization_index={self._real_id}" multiple times.

    async def _transmit_numerical_record(self, record: ert.data.NumericalRecord) -> str:
        url = f"{self._uri}/matrix"
        if self._real_id is not None:
            url = f"{url}?realization_index={self._real_id}"
            self._uri = f"{self._uri}?realization_index={self._real_id}"
        await add_record(url, record)
        return self._uri

    async def _transmit_blob_record(self, record: ert.data.BlobRecord) -> str:
        url = f"{self._uri}/file"
        if self._real_id is not None:
            url = f"{url}?realization_index={self._real_id}"
            self._uri = f"{self._uri}?realization_index={self._real_id}"
        await add_record(url, record)
        return self._uri

To Reproduce Supply a bad URL to the transmitter, should end up with …/realization_index=n?realization_index=n?realization_index=n?realization_index=n?.

Expected behavior Transmission should have no side effects on the transmitter object as far as these methods are concerned. State is mutated outside of these methods.