Change find_reversed_path function using the reversed_oms
Change find_reversed_path function using the reversed_oms

reversed_oms was introdused in order to identify which oms correspond
to the reversed direction of a given oms.
with this commit we make use of this functionality and avoid the cumbersome
way that recovered the reversed path by computing shortest path in the
reversed way for each roadm. This function could not support multiple links
in parallel between two roadms, and was adding computation time.

The function first lists the oms of the pth in the reversed order and then
appends all its elements to the path. the first and last elements are transponder
and are append separately.

Unidir topology are not supported: if there is no reversed path, this raises an error

Signed-off-by: EstherLerouzic <9136e9bbec0a09a1685b8ebbe677b6c9b26e8f18@orange.com>

Telecominfraproject/gnpy