LTP - realtime tests - fix bad robust mutex conditionals

LTP - realtime tests - fix bad robust mutex conditionals

The tests for robust mutexes contained conditional clauses which failed in
autoconf and/or used nonexistent variable names.  Modified these
conditional clauses to use only the variables actually created by
LTP autoconf for this purpose.

Signed-off-by: Gary S. Robertson <gary.robertson@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>