issues with pynbody profiles and server-shared-mem

[mtremmel]

When --load-mode=server-shared-mem is set and a calculation uses pynbody profiles, the profile object fails to recognize keys which are not already loaded as available. For example when attempting to make a metals profile, a profile object is created (pro_g for gas only) but pro_g['metals'] throws an error that the metals key is not seen as valid. This only occurs in tangos when this load mode is used. The current solution is to force pynbody to load in this data first, then ask for the profile (i.e. halo.g['metals'] before trying to calculate pro_g['metals'])