Fix range() usage on is_occupied() column check with barriers (#1727)
Fix range() usage on is_occupied() column check with barriers (#1727)

This commit fixes an issue with the latex output mode for the circuit
drawer when using barriers. The latex drawer maintains a list to track
which rows for a particular column are occupied or not. This can then be
used to determine whether or not we need to shift an element left or
right, this is especially necessary for multibit elements (ie
conditionals, measures, multi-qubit gates, and barriers). However, for
barriers there was a bug in the use of the range() function to determine
which rows to check. Instead of calling the function correctly with
range(start, stop) it was calling the function with range(start, len)
which is incorrect. This commit fixes this issue which means that now
drawing barriers will work correctly in cases where it previously did
not (and would overwrite circuit elements incorrectly)

Fixes #1724
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py