util: Remove logging handlers in virExec

This allows debug statements and raised errors in hook functions to
actually be logged somewhere (stderr). Users can enable debugging in the
daemon and now see more info in /var/log/libvirt/...

src/util/util.c

@@ -334,6 +334,7 @@ __virExec(virConnectPtr conn,
     int pipeerr[2] = {-1,-1};
     int childout = -1;
     int childerr = -1;
+    int logprio;
     sigset_t oldmask, newmask;
     struct sigaction sig_action;
 
@@ -452,6 +453,13 @@ __virExec(virConnectPtr conn,
        of being seen / logged */
     virSetErrorFunc(NULL, NULL);
 
+    /* Make sure any hook logging is sent to stderr, since virExec will
+     * close any unknown FDs (including logging handlers) before launching
+     * the new process */
+    logprio = virLogGetDefaultPriority();
+    virLogReset();
+    virLogSetDefaultPriority(logprio);
+
     /* Clear out all signal handlers from parent so nothing
        unexpected can happen in our child once we unblock
        signals */