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/log.c

@@ -48,9 +48,9 @@ static int log_max_level = LOG_INFO;
 static int log_facility = LOG_DAEMON;
 
 static int console_fd = STDERR_FILENO;
-static int syslog_fd = -1;
-static int kmsg_fd = -1;
-static int journal_fd = -1;
+static int syslog_fd = -EBADF;
+static int kmsg_fd = -EBADF;
+static int journal_fd = -EBADF;
 
 static bool syslog_is_stream = false;
 
@@ -345,7 +345,7 @@ void log_close(void) {
 void log_forget_fds(void) {
         /* Do not call from library code. */
 
-        console_fd = kmsg_fd = syslog_fd = journal_fd = -1;
+        console_fd = kmsg_fd = syslog_fd = journal_fd = -EBADF;
 }
 
 void log_set_max_level(int level) {