[DIRAC][v6r12] Fix FileBackend for Logger
Fix the constructor

Use super to be correct.
Fix the parent constructor call

fix the optionsDictionary setting
Fix the constructor

more fix
The method returns a bool
add default exitCode

As it isn't used, it shouldn't be needed.
Merge pull request #1973 from sposs/patch-3

[v6r12] Fix FileBackend for Logger