[1.12.2] Fix sidedness issues with TC & HWYLA integration

[jchung01]

This fixes client-only classes being class-loaded on a dedicated server. Functionally, there is no difference as the two integration modules are technically only handled client-side, but now the modules don't error when being registered on the dedicated server.
Thaumcraft error:

[Server thread/INFO] [chameleon]: Could not load integration module: com.jaquadro.minecraft.storagedrawers.integration.Thaumcraft

HWYLA/Waila error:

[Server thread/INFO] [Waila]: Registering plugin at com.jaquadro.minecraft.storagedrawers.integration.Waila
[Server thread/ERROR] [Waila]: Error registering wrapped plugin from storagedrawers at com.jaquadro.minecraft.storagedrawers.integration.Waila.registerProvider

Removes reflection usage, as it is not needed to access ConfigHandler.
Discovered in CleanroomMC/Cleanroom#349, as there are visible errors that arise from the bug in a Cleanroom environment.