Initialize variables in FindPeaks before passing by reference.

Fixes the GetDetOffsetsMultiPeaks unit test on Fedora 20, which was
discovered using valgrind and the --undef-value-errors=yes option.
Refs #9808
Retrieve result before deleting gsl structure.

Fixes an error found by valgrind.
Refs #9808
Merge branch 'bugfix/9808_failing_unittests_gcc48' into develop