tree-wide: use -EBADF for fd initialization

-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.

Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state

Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.

In some places, initialization is dropped if unnecessary.

src/basic/memfd-util.c

@@ -113,7 +113,7 @@ int memfd_set_size(int fd, uint64_t sz) {
 }
 
 int memfd_new_and_map(const char *name, size_t sz, void **p) {
-        _cleanup_close_ int fd = -1;
+        _cleanup_close_ int fd = -EBADF;
         int r;
 
         assert(sz > 0);