fix memory leaks detected by coverity.
fix memory leaks detected by coverity.

Winterflower/khmer,ged-lab/khmer,Winterflower/khmer,Winterflower/khmer,ged-lab/khmer,jas14/khmer,F1000Research/khmer,kdmurray91/khmer,kdmurray91/khmer,ged-lab/khmer,jas14/khmer,souravsingh/khmer,souravsingh/khmer,F1000Research/khmer,souravsingh/khmer,jas14/khmer,F1000Research/khmer,kdmurray91/khmer