fbarray: support --no-shconf mode

fbarray: support --no-shconf mode

When using --no-shconf option, the expectation is that no multiprocess
will be supported as no shared files are created. However, fbarray still
creates some shared files that prevent multiple processes with the same
prefix from starting.

Fix this by avoiding creating shared files whenever noshconf option is
specified. Since virtual areas we get from eal_get_virtual_area() are
read-only, remap them as writable.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>