Gross mass is not properly tied to the mission mass

[johnjasa]

Description

@kaushikponnapalli and I have been working through an issue that we noticed when examining on/off-design capabilities.

The default phase_info for height_energy currently has optimize_mass=True and fix_initial=True.
This means that the mass state in the Dymos mission is fixed to be whatever the initial value is, set by the initial guessing.
This is not forced to be the same as Aircraft.Design.GROSS_MASS, so those values can vary.
They should not be allowed to vary; this is a bug.
This only occurs when include_takeoff=False; if that is True, then the initial mass is set correctly.

Example

See description; run a basic Aviary example with height energy

Aviary Version

0.9.4-dev

Relevant environment information

No response