The guest may assume FBOs are complete that actually fail on the host side

With softpipe on the host some dEQP-GLES3 tests have random results because the FBOs created by the test are incomplete with FRAMEBUFFER_UNSUPPORTED. When run directly on the softpipe host the tests fail consistently because of this, but when run through virgl these tests don't get such an error message and assume that the results that are read back are valid.

It seems that the guest assumes host support for something that is actually not supported, i.e. the caps needed to create these FBOs are not communicated correctly.