shutdown: Add Xen kexec support

In the Xen case, it's the hypervisor which manages kexec. We thus
have to ask it whether a kernel is loaded, instead of relying on
/sys/kernel/kexec_loaded.

src/basic/util.c

@@ -23,15 +23,6 @@ int saved_argc = 0;
 char **saved_argv = NULL;
 static int saved_in_initrd = -1;
 
-bool kexec_loaded(void) {
-       _cleanup_free_ char *s = NULL;
-
-       if (read_one_line_file("/sys/kernel/kexec_loaded", &s) < 0)
-               return false;
-
-       return s[0] == '1';
-}
-
 int prot_from_flags(int flags) {
 
         switch (flags & O_ACCMODE) {

src/basic/util.h

@@ -19,8 +19,6 @@ static inline void save_argc_argv(int argc, char **argv) {
         saved_argv = argv;
 }
 
-bool kexec_loaded(void);
-
 int prot_from_flags(int flags) _const_;
 
 bool in_initrd(void);