release will not update if kernel name is anything other than kernel

[woodsb02]

On iocell 2.1.0, if sysctl -n kern.bootfile is not /boot/kernel/kernel then running "iocell fetch" will fail to perform a freebsd-update.

# iocell fetch release=11.0-RELEASE
Extracting: base.txz
Extracting: doc.txz
Extracting: lib32.txz
Extracting: src.txz
* Updating base jail template.
Cannot identify running kernel
No updates are available to install.
Run '/usr/sbin/freebsd-update fetch' first.

The reason is explained in this forum post: https://forums.freebsd.org/threads/43329/#post-241491

The solution is to ensure the release contains the directory sysctl -n kern.bootfile:

# cd /iocell/releases/11.0-RELEASE/root/boot/
# ln -sf kernel `sysctl -n kern.bootfile`

[rwp0]

freebsd-update(8) source contains:

	# Figure out what directory contains the running kernel
	BOOTFILE=`sysctl -n kern.bootfile`
	KERNELDIR=${BOOTFILE%/kernel}
	if ! [ -d ${KERNELDIR} ]; then
		echo "Cannot identify running kernel"
		exit 1
	fi

Which produces Cannot identify running kernel message for all kernel files named other than plain kernel.

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This code snippet is repeated three times in the shell script making it a good candidate to wrap in a function.