util: virfile: Drop QB_MAGIC constant

util: virfile: Drop QB_MAGIC constant

The filesystem type magic constant was added for the 'quobyte' shared
filesystem in commit 451094bd153 but is present neither in the kernel
sources nor in coreutils which we've historically used as source of
information.

Since the code dealing with FUSE-based filesystems doesn't need the
constant we can remove it and the now-dead check for it.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>