tests/export/hazard_test:

Added a test to prove that
https://bugs.launchpad.net/oq-engine/+bug/1202290 exists.
export/hazard:

Refactored metadata handling in hazard curv and hazard curve multi
exporters.
export/hazard:

Added explicit support for hazard_curve_multi outputs in
_get_result_export_dest.
tests/export/hazard_test:

Added a hazard_curve_multi test case to `_get_result_export_dest` tests.
Merge pull request #1271 from larsbutler/fix-haz-curve-multi-export-path

Fix hazard_curve_multi export path

[r=matley] [f=1202290]