PIMutexUnlock: load owner_tid in non-common case

For a recursive or errorcheck PI mutex, the old_owner variable wasn't
being initialized. As a result, unlocking a doubly-locked recursive
mutex owned by another thread decremented the mutex counter. Instead, the
unlock call should fail with EPERM.

Bug: http://b/130841532
Test: bionic-unit-tests
Test: bionic-unit-tests-glibc --gtest_filter='pthread.pthread_mutex_lock*'
Change-Id: I37adb094cb2ce8d51df7b4f48e8d6bc144436418
(cherry picked from commit 4b6c0f5dce5ad8d93e4e707977e09153a5399139)