LinuxOptions.BindMountPersistentDisk used for tmpfs mounts

[sykesm]

The agent settings for the linux platform includes the following:

	// When set to true persistent disk will be mounted as a bind-mount
	BindMountPersistentDisk bool

When that option is enabled, it uses the linuxBindMounter for more than persistent disks. In my case, it's attempting to create and mount a tmpfs at /var/vcap/data/sys/run with the --bind option; this doesn't work:

2016-11-17_19:56:25.34094 [main] 2016/11/17 19:56:25 ERROR - App setup Running bootstrap: Setting up data dir: Mounting tmpfs to /var/vcap/data/sys/run: Shelling out to mount: Running command: 'mount tmpfs /var/vcap/data/sys/run -t tmpfs -o size=1m --bind', stdout: '', stderr: 'mount: special device tmpfs does not exist
2016-11-17_19:56:25.34095 ': exit status 32
2016-11-17_19:56:25.34098 [main] 2016/11/17 19:56:25 ERROR - Agent exited with error: Running bootstrap: Setting up data dir: Mounting tmpfs to /var/vcap/data/sys/run: Shelling out to mount: Running command: 'mount tmpfs /var/vcap/data/sys/run -t tmpfs -o size=1m --bind', stdout: '', stderr: 'mount: special device tmpfs does not exist
2016-11-17_19:56:25.34099 ': exit status 32

Mounting without the bind option works:

/:/var/vcap/bosh# mount tmpfs /var/vcap/data/sys/run -t tmpfs -o size=1m       
/:/var/vcap/bosh# ls -l /var/vcap/data/sys/
total 4
drwxr-x--- 2 root vcap 4096 Nov 17 19:53 log
drwxrwxrwt 2 root root   40 Nov 17 21:52 run
/:/var/vcap/bosh#                                                       

[cppforlife]

i think this was fixed some time ago in 3363.x stemcells: https://github.com/cloudfoundry/bosh-agent/blob/master/platform/disk/linux_bind_mounter.go#L13