various: do not include file names directly in error messages

git grep -l 'Failed to open /'|xargs sed -r -i 's|"Failed to open (/[^ ]+): %m"|"Failed to open %s: %m", "\1"|g'
git grep -l $'Failed to open \'/'|xargs sed -r -i $'s|"Failed to open \'(/[^ ]+)\': %m"|"Failed to open %s: %m", "\\1"|g'
git grep -l "Failed to open /"|xargs sed -r -i $'s|"Failed to open (/[^ ]+), ignoring: %m"|"Failed to open %s, ignoring: %m", "\\1"|g'
+ some manual fixups.

src/shutdown/detach-dm.c

@@ -109,7 +109,7 @@ static int delete_dm(DeviceMapper *m) {
 
         fd = open("/dev/mapper/control", O_RDWR|O_CLOEXEC);
         if (fd < 0)
-                return log_debug_errno(errno, "Failed to open /dev/mapper/control: %m");
+                return log_debug_errno(errno, "Failed to open %s: %m", "/dev/mapper/control");
 
         return RET_NERRNO(ioctl(fd, DM_DEV_REMOVE, &(struct dm_ioctl) {
                 .version = {

src/shutdown/shutdown.c

@@ -197,7 +197,7 @@ static int sync_making_progress(unsigned long long *prev_dirty) {
 
         f = fopen("/proc/meminfo", "re");
         if (!f)
-                return log_warning_errno(errno, "Failed to open /proc/meminfo: %m");
+                return log_warning_errno(errno, "Failed to open %s: %m", "/proc/meminfo");
 
         for (;;) {
                 _cleanup_free_ char *line = NULL;

src/shutdown/umount.c

@@ -188,7 +188,7 @@ static void log_umount_blockers(const char *mnt) {
 
         _cleanup_closedir_ DIR *dir = opendir("/proc");
         if (!dir)
-                return (void) log_warning_errno(errno, "Failed to open /proc/: %m");
+                return (void) log_warning_errno(errno, "Failed to open %s: %m", "/proc/");
 
         FOREACH_DIRENT_ALL(de, dir, break) {
                 if (!IN_SET(de->d_type, DT_DIR, DT_UNKNOWN))