UTIL: Use a custom PID_PATH and DB_PATH when unit testing server.c
server.c used hardcoded PID_PATH and DB_PATH from config.h. Normally,
this path resides in a system directory (like /var/) and should not be
written to by tests. In order to specify a different one for tests, we
need to conditionalize normal builds and unit test builds.
Reviewed-by: Pavel Reichl <email@example.com>