Using nonNull API's in ELAN

Using nonNull API's in ELAN

Description:

using nonnull version of API provided(Ex as below) before
doing .values() on the return value(applicable for all modules).
This can result in NPE.

    @Nullable
    List<Interfaces> getInterfaces();

    @NonNull
    default List<Interfaces> nonnullInterfaces() {
        return CodeHelpers.nonnull(this.getInterfaces());
    }

Changes done in ELAN to use nonnull version of API

JIRA:NETVIRT-1671

Signed-off-by: Chetan Arakere Gowdru <chetan.arakere@altencalsoftlabs.com>
Change-Id: I795c8f217d6de35841baf6847aa0e8929d02cc87
Signed-off-by: Chetan Arakere Gowdru <chetan.arakere@altencalsoftlabs.com>