linux: use IS_VALID_LLDB_HOST_THREAD.

Update the linux plugin code to use the new check for a valid host
thread introduced in r125067.

llvm-svn: 125213
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index 2c93638..490ca6f 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -555,7 +555,7 @@
     // Finally, start monitoring the child process for change in state.
     m_monitor_thread = Host::StartMonitoringChildProcess(
         ProcessMonitor::MonitorCallback, this, GetPID(), true);
-    if (m_monitor_thread == LLDB_INVALID_HOST_THREAD)
+    if (!IS_VALID_LLDB_HOST_THREAD(m_monitor_thread))
     {
         error.SetErrorToGenericError();
         error.SetErrorString("Process launch failed.");
@@ -580,7 +580,7 @@
 {
     static const char *g_thread_name = "lldb.process.linux.operation";
 
-    if (m_operation_thread != LLDB_INVALID_HOST_THREAD)
+    if (IS_VALID_LLDB_HOST_THREAD(m_operation_thread))
         return;
 
     m_operation_thread =
@@ -592,7 +592,7 @@
 {
     lldb::thread_result_t result;
 
-    if (m_operation_thread == LLDB_INVALID_HOST_THREAD)
+    if (!IS_VALID_LLDB_HOST_THREAD(m_operation_thread))
         return;
 
     Host::ThreadCancel(m_operation_thread, NULL);
@@ -1009,7 +1009,7 @@
 {
     lldb::thread_result_t thread_result;
 
-    if (m_monitor_thread != LLDB_INVALID_HOST_THREAD)
+    if (IS_VALID_LLDB_HOST_THREAD(m_monitor_thread))
     {
         Host::ThreadCancel(m_monitor_thread, NULL);
         Host::ThreadJoin(m_monitor_thread, &thread_result, NULL);