This function is used only from code compiled on Linux. Therefore
on non-Linux platforms it triggers compilation error:

../../src/qemu/qemu_domain.c:209:1: error: unused function 'qemuDomainGetPreservedMounts' [-Werror,-Wunused-function]
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>