Ensure Texture always binds to self

Bug: 26584230

In the event that Texture decides it doesn't
need to actually call glTexImage2D/glSubTexImage2D
it needs to still activateTexture(0) and bindTexture(mId)
as this is the expected state after Texture::upload()
is called.

Change-Id: I62d689a9057907a10dda2bc8f40c3113e43b93b2