shared: Fix segfault in buxton_debug call

We've now changed to BuxtonString instead of using char* everywhere,
so this would segfault with --enable-debug (printing a type, not a
string)

Signed-off-by: Michael Ikey Doherty <michael.i.doherty@intel.com>
Verify that socket recieved strings end with 0x00

This commit ensures we ignore messages sending BuxtonString's that aren't
null terminated, treating them as garbage.

Signed-off-by: Michael Ikey Doherty <michael.i.doherty@intel.com>