Display more verbose error message when Nvidia encoding session limit exceeded

[cyberj0g]

Issue

When driver-imposed limit on number of parallel encoding sessions on Nvidia GPU is reached, obscure error message Could not allocate memory is displayed. We need to detect such situation and display clear error message, because, currently, launching T on any consumer Nvidia GPU with -nvidia flag will fail initial capability test, which attempts to transcode to 4 renditions.

Proposed fix

In case of error in TestTranscoderCapabilities, which is called on T startup, we need to check whether the error is persistent after decreasing number of renditions to 3, which is a limit on consumer Nvidia GPUs, and display correct error message, if it worked.