Do nor clear caps when invoking virt-aa-helper

The calls to virExec() in security_apparmor.c when
invoking virt-aa-helper use VIR_EXEC_CLEAR_CAPS. When compiled without
libcap-ng, this is not a problem (it's effectively a no-op) but with
libcap-ng this causes MAC_ADMIN to be cleared. MAC_ADMIN is needed by
virt-aa-helper to manipulate apparmor profiles and without it VMs will
not start[1]. This patch calls virExec with the default VIR_EXEC_NONE
instead.
* src/security/security_apparmor.c: fallback to VIR_EXEC_NONE flags for
  virExec of virt_aa_helper

src/security/security_apparmor.c

@@ -174,19 +174,19 @@ load_profile(const char *profile, virDomainObjPtr vm,
             VIRT_AA_HELPER, "-c", "-u", profile, NULL
         };
         ret = virExec(argv, NULL, NULL, &child,
-                      pipefd[0], NULL, NULL, VIR_EXEC_CLEAR_CAPS);
+                      pipefd[0], NULL, NULL, VIR_EXEC_NONE);
     } else if (disk && disk->src) {
         const char *const argv[] = {
             VIRT_AA_HELPER, "-r", "-u", profile, "-f", disk->src, NULL
         };
         ret = virExec(argv, NULL, NULL, &child,
-                      pipefd[0], NULL, NULL, VIR_EXEC_CLEAR_CAPS);
+                      pipefd[0], NULL, NULL, VIR_EXEC_NONE);
     } else {
         const char *const argv[] = {
             VIRT_AA_HELPER, "-r", "-u", profile, NULL
         };
         ret = virExec(argv, NULL, NULL, &child,
-                      pipefd[0], NULL, NULL, VIR_EXEC_CLEAR_CAPS);
+                      pipefd[0], NULL, NULL, VIR_EXEC_NONE);
     }
     if (ret < 0)
         goto clean;