fix bugs from Spotbugs report

src/main/java/gov/usgs/earthquake/nshmp/DeaggCalc.java

src/main/java/gov/usgs/earthquake/nshmp/DeaggEpsilon.java

src/main/java/gov/usgs/earthquake/nshmp/DeaggIml.java

src/main/java/gov/usgs/earthquake/nshmp/Hazard2018.java

src/main/java/gov/usgs/earthquake/nshmp/HazardCalc.java

src/main/java/gov/usgs/earthquake/nshmp/RateCalc.java

.../usgs/earthquake/nshmp/aws/HazardResultsSlicerLambda.java

...va/gov/usgs/earthquake/nshmp/www/DeaggEpsilonService.java