tools/kvm_stat: re-animate display of dead guests

When filtering by guest (interactive commands 'p'/'g'), and the respective
guest was destroyed, detect when the guest is up again through the guest
name if possible.
I.e. when displaying events for a specific guest, it is not necessary
anymore to restart kvm_stat in case the guest is restarted.

Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

tools/kvm/kvm_stat/kvm_stat

@@ -1103,6 +1103,7 @@ class Tui(object):
             pid = self.stats.pid_filter
         self.screen.erase()
         gname = self.get_gname_from_pid(pid)
+        self._gname = gname
         if gname:
             gname = ('({})'.format(gname[:MAX_GUEST_NAME_LEN] + '...'
                                    if len(gname) > MAX_GUEST_NAME_LEN
@@ -1170,6 +1171,15 @@ class Tui(object):
             return sorted_items
 
         if not self._is_running_guest(self.stats.pid_filter):
+            if self._gname:
+                try: # ...to identify the guest by name in case it's back
+                    pids = self.get_pid_from_gname(self._gname)
+                    if len(pids) == 1:
+                        self._refresh_header(pids[0])
+                        self._update_pid(pids[0])
+                        return
+                except:
+                    pass
             self._display_guest_dead()
             # leave final data on screen
             return