Tighten permissions for /run/initramfs

/run/initramfs contains a log file from fsck of root file system,
which could perhaps contain sensitive information, for example if
/home or /var are also located there and fsck is triggered.

Let's tighten the permissions to 0700.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>

init

@@ -208,7 +208,7 @@ else
 fi
 
 mount -t tmpfs -o "nodev,noexec,nosuid,size=${RUNSIZE:-10%},mode=0755" tmpfs /run
-mkdir -m 0755 /run/initramfs
+mkdir -m 0700 /run/initramfs
 
 if [ -n "$log_output" ]; then
 	exec >$log_output 2>&1