Entry-exit stubs are independent of deoptimization

We were incorrectly marking the instrumentation system as having no
instrumentation_stubs_installed_ even if entry_exit_stubs are still
installed. This would happen when the last method that had been
deoptimized is undeoptimized.

Test: ./test/testrunner/testrunner.py --host --runtime-option=-Xplugin:libtracefast-trampolined.so
Test: ./test.py --host

Change-Id: Ib3267cea65cb9f86f737eb5eb8b933daf76119b5