Use &error_fatal when initializing crypto on qemu-{img,io,nbd}

In addition to making the code simpler, this will replace the
long error messages:
  cannot initialize crypto: Unable to initialize GNUTLS library: [...]
  cannot initialize crypto: Unable to initialize gcrypt
with shorter messages:
  Unable to initialize GNUTLS library: [...]
  Unable to initialize gcrypt

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

qemu-img.c

@@ -3492,10 +3492,7 @@ int main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
-    if (qcrypto_init(&local_error) < 0) {
-        error_reportf_err(local_error, "cannot initialize crypto: ");
-        exit(1);
-    }
+    qcrypto_init(&error_fatal);
 
     module_call_init(MODULE_INIT_QOM);
     bdrv_init();

qemu-io.c

@@ -466,10 +466,7 @@ int main(int argc, char **argv)
     progname = basename(argv[0]);
     qemu_init_exec_dir(argv[0]);
 
-    if (qcrypto_init(&local_error) < 0) {
-        error_reportf_err(local_error, "cannot initialize crypto: ");
-        exit(1);
-    }
+    qcrypto_init(&error_fatal);
 
     module_call_init(MODULE_INIT_QOM);
     qemu_add_opts(&qemu_object_opts);

qemu-nbd.c

@@ -527,10 +527,7 @@ int main(int argc, char **argv)
     sa_sigterm.sa_handler = termsig_handler;
     sigaction(SIGTERM, &sa_sigterm, NULL);
 
-    if (qcrypto_init(&local_err) < 0) {
-        error_reportf_err(local_err, "cannot initialize crypto: ");
-        exit(1);
-    }
+    qcrypto_init(&error_fatal);
 
     module_call_init(MODULE_INIT_QOM);
     qemu_add_opts(&qemu_object_opts);