Invalid gain values in simulator

[graeme-winter]

*Distribution:

RHEL8 but this is not pertinent to the issue.

*Detector type:

Jungfrau SIMULATOR

*Software Package Version:

Current main

Priority:

Low

*Describe the bug

Invalid gain values in the simulated pixels:

        for (int i = 0; i < npixels; ++i) {
            if (i % pixelsPerPacket == 0) {
                ++dataVal;
            }

            if ((i % 1024) < 300) {
                gainVal = 1;
            } else if ((i % 1024) < 600) {
                gainVal = 2;
            } else {
                gainVal = 3;
            }
            pixelVal = (dataVal & ~GAIN_VAL_MSK) | (gainVal << GAIN_VAL_OFST);
        }

My understanding is that the legal values for the gain bits are 0, 1 and 3.

Expected behavior

The gain values correspond to the legal values

To Reproduce

Run the simulator

Additional context

I'll put a PR in to address this.