Tests: Add missing mockup function to tests

void async_config(void) {}

void async_dump(void) {}

void async_shutdown(void) {}

char *get_hostname(linpool *lp UNUSED) { return NULL; }

void cmd_check_config(char *name UNUSED) {}

void cmd_reconfig(char *name UNUSED, int type UNUSED, int timeout UNUSED) {}

void cmd_reconfig_confirm(void) {}