Oscillating collimator: check and turn motor on before moving

to `c:\Instrument\Apps\EPICS\support\galil-old\master\gmc\galil_oscillating_collimator.gmc` (note: `galil-old`) in the `#OSCIL` step need to turn motor on. Could change `BG~a` to `SH~a;BG~a` but I know we often do `SH~a;WT100;BG~a` but i am not sure we want to introduce a delay. The motor should already be on, so in case a rapid SH;BG can potentially cause an issue maybe safest to add something like this to the top of `#OSCIL`:
```
IF (_MO~a = 1)
SH~a; WT100
ENDIF
```

In addition, it does not e.g. check stop `_SC~a` after a move, or limit switch status e.g. `_LR~a` and `_LF~a` or have a `#LIMSWI` routine like in `galil_default_footer`. May be worth putting setting an error variable in controller if `_SC` shows move doesn't complete and then exposing this variable to DB

## acceptance criteria
- patched on LET
- merged into master