Make program separable in TCS-but-no-TES draw time check test.

Make program separable in TCS-but-no-TES draw time check test.

Section 7.3 of the OpenGL ES 3.2 specification says:

   "Linking can fail for [...] any of the following reasons:

    * program contains an object to form a tessellation control
      shader [...] and [...] the program is not separable and
      contains no object to form a tessellation evaluation shader"

Since the test is trying to check for a draw time error, it should use
a separable program - otherwise we may hit a link error.

Fixes a bug in:
dEQP-GLES31.functional.debug.negative_coverage.*.tessellation.single_tessellation_stage

Change-Id: Ida906e21c3e3534fd2a8c7bac0334083881bdb19