podman: podman cannot mount volumes with external symlinks

/kind bug

Description

Podman volumes with external symlinks does not seem to be mountable

Steps to reproduce the issue:

1. Create volume with symlink which references files outside of the volume. For example symbolic link to …/foo

2. Try to mount the volume.

3. Volume does not mount

Describe the results you received: Volume fails to mount

Describe the results you expected:

Volume should mount, and when I enter the image, I should see the symbolic link point to the file within the context of the mounted volume. This is the behavior in docker. Also these sorts of symbolic links are very common in directory /etc which points to /usr/share or to other directories outside the volume

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Error: unable to start container 34e9c7636cd474d63741b93ecbd0dabfcab44aad263cedac4b4aa65ef93c5460: error copying content from container 34e9c7636cd474d63741b93ecbd0dabfcab44aad263cedac4b4aa65ef93c5460 into volume demo_etc: invalid symlink “/home/joe/.local/share/containers/storage/volumes/demo_etc/_data/httpd/logs” -> “…/…/var/log/httpd”

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Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version: [joe@big-apple bench]$ podman version Version: 2.0.0-dev RemoteAPI Version: 1 Go Version: go1.14.2 OS/Arch: linux/amd64

**Output of `podman info --debug`:**

[joe@big-apple SPECS]$ 
  configFile: /home/joe/.config/containers/storage.conf
  containerStore:
    number: 9
    paused: 0
    running: 5
    stopped: 4
  graphDriverName: vfs
  graphOptions: {}
  graphRoot: /home/joe/.local/share/containers/storage
  graphStatus: {}
  imageStore:
    number: 36
  runRoot: /run/user/1000/containers
  volumePath: /home/joe/.local/share/containers/storage/volumes
version:
  Built: 0
  GitCommit: ""
  GoVersion: go1.14.2
  OsArch: linux/amd64
  RemoteAPIVersion: 1
  Version: 2.0.0-dev

Package info (e.g. output of rpm -q podman or apt list podman):

podman-2.0.0-0.1.dev.git8857ba2.mga8

Additional environment details (AWS, VirtualBox, physical, etc.):