libhsakmt: Improve error handling in child process

Check for errno == EBADF in kmtIoctl to detect misuse of the kfd_fd
in a forked child process.

Detect being in a forked child process pro-actively by implementing
a pthread_atfork callback.

Make sure all mutexes get reinitialized in the child process to avoid
deadlocks.

Check for being in a forked child process in CHECK_KFD_OPENED so that
all hsaKmt functions will return the appropriate status
HSAKMT_STATUS_KERNEL_IO_CHANNEL_NOT_OPENED.

Update InvalidKFDHandleTest to expect that error code.

Change-Id: I0238e5fba344dcaa454e97a35db2e2dcc8d1f607
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>

tests/kfdtest/src/KFDOpenCloseKFDTest.cpp

@@ -75,7 +75,7 @@ TEST_F(KFDOpenCloseKFDTest, InvalidKFDHandleTest ) {
     HsaVersionInfo  m_VersionInfo;
     pid_t m_ChildPid = fork();
     if (m_ChildPid == 0) {
-        EXPECT_EQ(HSAKMT_STATUS_ERROR, hsaKmtGetVersion(&m_VersionInfo));
+        EXPECT_EQ(HSAKMT_STATUS_KERNEL_IO_CHANNEL_NOT_OPENED, hsaKmtGetVersion(&m_VersionInfo));
         exit(0);
     } else {
         int childStatus;