fix issue #3423: context to move back motors at the end of the scan, now only considers real axes
requested to merge 3423-d2scan-not-moving-motors-of-both-motors-back-to-original-position-after-ctrl-c-or-another-error_1.10.x into 1.10.x
In the case of interrupted 'dscan' of slits offset (for exemple), the gap changes while blades are moving - when interrupting the scan, moving back offset is not enough to restore position. We can avoid this sort of problem by moving back real motors to the start position instead of moving calc axes. It is enough to look at real axes at first level of depth.
Closes #3423 (closed)