Remove spurious call to unix_physmem_init(...)

Remove spurious call to unix_physmem_init(...)

It turns out that unix_physmem_init(...) has been effectively disabled
for a very long time. The vnet library supplied a weak symbol override
for the vlib_app_physmem_init(...) which returned 1, meaning "do
nothing." When we switched libvnet.a -> libvnet.so, the symbol
override stopped working.

Presto: unix_physmem_init(...) romps all over the data set up by
vlib_buffer_pool_create(...), leading to ASSERT failures and/or bus
errors, but only when using worker threads. Even then, the failure
depended in some complicated way on library dynamic load order.

We should remove .../vlib/vlib/unix/physmem.c entirely once we're sure
we'll never want it back.

Change-Id: I27747edbeb0de88d2f2d8728f7f8eb3135e7f0cf
Signed-off-by: Dave Barach <dave@barachs.net>