CLIMATE-332 - Add initial metric loading test
CLIMATE-332 - Add initial metric loading test

- Remove relative imports of backend modules.
- Move local dataset setUp and tearDown methods out of module scope.
- Add test for get_valid_metric_options.

git-svn-id: https://svn.apache.org/repos/asf/incubator/climate/trunk@1566127 13f79535-47bb-0310-9956-ffa450edef68

Former-commit-id: aaa786906e21913a1d28c45cfd9e73258bcb79d9
agoodm/climate,MJJoyce/climate,MBoustani/climate,lewismc/climate,Omkar20895/climate,Omkar20895/climate,kwhitehall/climate,jarifibrahim/climate,jarifibrahim/climate,huikyole/climate,riverma/climate,MBoustani/climate,agoodm/climate,jarifibrahim/climate,lewismc/climate,Omkar20895/climate,riverma/climate,huikyole/climate,MJJoyce/climate,Omkar20895/climate,huikyole/climate,agoodm/climate,apache/climate,kwhitehall/climate,MBoustani/climate,apache/climate,riverma/climate,riverma/climate,kwhitehall/climate,jarifibrahim/climate,MJJoyce/climate,pwcberry/climate,pwcberry/climate,lewismc/climate,agoodm/climate,apache/climate,MBoustani/climate,MJJoyce/climate,apache/climate,lewismc/climate,huikyole/climate,riverma/climate,MBoustani/climate,pwcberry/climate,huikyole/climate,agoodm/climate,lewismc/climate,Omkar20895/climate,kwhitehall/climate,jarifibrahim/climate,pwcberry/climate,apache/climate,MJJoyce/climate,pwcberry/climate