use gtest asserts in ProcessGroupGlooTest instead of other checks (#32138)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32138
I personally prefer `throw std::runtime_error("BOOM")`, but we should
probably have asserts here now that it is gtest. Also ensures that the correct
exceptions are thrown by the `testSignal` tests.
ghstack-source-id: 96811000
Differential Revision: D19382905
fbshipit-source-id: 1b00dd70524d03c8bd6f48715baa5070a7985467
