library: revert changes to 'look_up_our_self' function

The patch below is where most proc_t fixed size arrays
became simple pointers to char. In that commit changes
to the above function were made so that dynamic memory
was freed which included the program name (cmd) field.

That change was prompted by a valgrind reported memory
leak during development that no longer seems to exist.
However, by keeping the look_up_our_self() changes the
ps command without args then fails to report anything.

So this patch just restores the expected old behavior.

Reference(s):
commit 3881a0844a

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/readproc.c

@@ -1426,9 +1426,7 @@ void look_up_our_self(proc_t *p) {
         fprintf(stderr, "Error, do this: mount -t proc proc /proc\n");
         _exit(47);
     }
-    memset(p, 0, sizeof(*p));
     stat2proc(ub.buf, p);  // parse /proc/self/stat
-    free_acquired(p, 0);
     free(ub.buf);
 }