Fix crash when deleting DrawableManager while a Scene is being attached

Change-Id: I2fc2631e5a7389ded9b10bc864bb62694e74a148
Reviewed-on: http://git-master/r/558306
Reviewed-by: Markus Tavenrath <matavenrath@nvidia.com>
Tested-by: Markus Tavenrath <matavenrath@nvidia.com>
Reviewed-by: Andreas Suessenbach <asuessenbach@nvidia.com>
Tested-by: Andreas Suessenbach <asuessenbach@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Detlef Roettger <droettger@nvidia.com>
Tested-by: Detlef Roettger <droettger@nvidia.com>
Use GL_NV_uniform_buffer_unified_memory in dp::rix::gl if it is available

Change-Id: I6bec875826861bef1753840b34928e2cb80589a7
Reviewed-on: http://git-master/r/559382
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Andreas Suessenbach <asuessenbach@nvidia.com>
Reviewed-by: Markus Tavenrath <matavenrath@nvidia.com>
Tested-by: Markus Tavenrath <matavenrath@nvidia.com>