Bug 1640448

By default the expire of automounted mounts depends on the last access. In very large environments this helps reduce the number of mount requests from clients which can be significant. But this can lead to mounts not being umounted when monitoring services scan directory trees containing automounts. In this case it can be beneficial to expire mounts based on whether they are actually in use (ie. contain a process working directory of open files), the so-called strict expire. To allow for this later case a master map entry mount option, strictexpire, has been added. This mount option causes mounts to expire based on whether they are actually in use. To enable this behaviour the mount option "strictexpire" needs to be added to automount master map entries and the expire behaviour will change if the kernel in use supports it.