Remove while loop to avoid infinite loop
Remove while loop to avoid infinite loop

In the previous implementation, when a constraint was added on top of
the disjunction, there could be an infinite loop because the test was
not correctly performed on the request_id but on a request class.
Moreover, there the loop was not needed since the first feasible
candidate is selected if it exist.
This patch removes the loop and adds some comments to explain the code.

Signed-off-by: EstherLerouzic <9136e9bbec0a09a1685b8ebbe677b6c9b26e8f18@orange.com>
Change-Id: Icdbee9032f28214b3e03cb62d55ea353477d94bf

Telecominfraproject/gnpy