set the backend in "startDevelopment" mode always to curl

Since the following refactoring in qafoolabs/profiler:
https://github.com/QafooLabs/profiler/commit/b1825a8148318b415eedb174a9a306faa4c46410#diff-59439c0ee27bc5dbf57d3a5d902a6953R256

curl is only used if given explicitely via the method parameter
of the trigger-profile-header/get-params. However, we always
want to use the curl backend in startDevelopment mode, since
these environments don't have the daemon installed anyway.