Clean up JuMP code in tests

[odow]

This smells like JuMP 0.18: https://github.com/lanl-ansi/Juniper.jl/blob/df63a8d41b699be47d1eeecacef3ec2a6572c0e4/test/runtests.jl#L51-L70

[Wikunia]

Can you refer to what changed regarding this? I'm a bit out of the loop 😃 are there new ways to obtain the inner model now?

[odow]

solve is optimize!, followed by termination_status internalmodel is unsafe_backend getsolvetime is solve_time getobjgap is relative_gap