Fix Bug 826 Regression caused by commit 41190c3830157abdf9649cbf7767e57108f55075 (Bug 975)

Commit 41190c3830157abdf9649cbf7767e57108f55075,
fix for 'Bug 975 GLJPanel's OffscreenDrawable double swap',
caused a regression of commit c427ed22244df44b71a0f1f000b0f93e56c283c2,
fix for 'Bug 826: GLJPanel: Fully restore TextureState and Viewport'.

Commit 41190c3830157abdf9649cbf7767e57108f55075 issues offscreenDrawable.swapBuffers()
and hence modifying the texture unit settings before saving the TextureState,
the whole purpose of commit c427ed22244df44b71a0f1f000b0f93e56c283c2.