Remove some redundant variables and assignments.

This fixes a batch of clang-analyzer warnings of the form 'you
declared / assigned this variable and then never use it'. It doesn't
fix _all_ of them - some are there so that when I add code in the
future _it_ can use the variable without me having to remember to
start setting it - but these are the ones I thought it would make the
code better instead of worse to fix.

unix/uxnet.c

@@ -794,7 +794,6 @@ Socket *sk_new(SockAddr *addr, int port, bool privport, bool oobinline,
     ret->privport = privport;
     ret->port = port;
 
-    err = 0;
     do {
         err = try_connect(ret);
     } while (err && sk_nextaddr(ret->addr, &ret->step));