Description of problem:
During the leapp upgrade, customer reported the following issue:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 72, in _do_run
    actor_instance.run(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/actors/__init__.py", line 335, in run
    self.process(*args)
  File "/usr/lib/python2.7/site-packages/leapp/utils/deprecation.py", line 42, in process_wrapper
    return target_item(*args, **kwargs)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/targetuserspacecreator/actor.py", line 43, in process
    userspacegen.perform()
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/targetuserspacecreator/libraries/userspacegen.py", line 478, in perform
    _create_target_userspace(context, indata.packages, target_repoids)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/targetuserspacecreator/libraries/userspacegen.py", line 457, in _create_target_userspace
    _prep_repository_access(context, constants.TARGET_USERSPACE)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/targetuserspacecreator/libraries/userspacegen.py", line 144, in _prep_repository_access
    context.copytree_from('/etc/pki', os.path.join(target_userspace, 'etc', 'pki'))
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/libraries/mounting.py", line 198, in copytree_from
    shutil.copytree(self.full_path(src), dst)
  File "/usr/lib64/python2.7/shutil.py", line 208, in copytree
    raise Error, errors
Error: [('/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/tls/certs/57dcc1cc.0', '/var/lib/leapp/el8userspace/etc/pki/tls/certs/57dcc1cc.0', "[Errno 2] No such file or directory: '/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/tls/certs/57dcc1cc.0'"), ('/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/pulp/content/e097f848.r0', '/var/lib/leapp/el8userspace/etc/pki/pulp/content/e097f848.r0', "[Errno 2] No such file or directory: '/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/pulp/content/e097f848.r0'"), ('/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/pulp/content/pulp-global-repo.ca', '/var/lib/leapp/el8userspace/etc/pki/pulp/content/pulp-global-repo.ca', "[Errno 2] No such file or directory: '/var/lib/leapp/scratch/mounts/root_/system_overlay/etc/pki/pulp/content/pulp-global-repo.ca'")]

As per the `ls -lR /etc/pki` output, the following relative symlinks are broken:
	/etc/pki/pulp/content:
	total 0
	lrwxrwxrwx. 1 root root 36 May 29  2018 e097f848.r0 -> /var/lib/candlepin/candlepin-crl.crl
	lrwxrwxrwx. 1 root root 20 May 29  2018 pulp-global-repo.ca -> /etc/pki/pulp/ca.crt

	/etc/pki/tls/certs:
	total 48
	lrwxrwxrwx. 1 root root   29 May 15  2017 57dcc1cc.0 -> subscriptionrhsmredhatcom.pem

Version-Release number of selected component (if applicable):
leapp-repository-0.14.0-4.el7_9

How reproducible:
100%

Steps to Reproduce:

	# mkdir -p /etc/pki/pulp/content
	# cd /etc/pki/pulp/content
	# ln -s ../ca.crt pulp-global-repo.ca
	# ls /etc/pki/pulp/ca.crt
	ls: cannot access /etc/pki/pulp/ca.crt: No such file or directory
	# leapp upgrade

Actual results:
Python traceback above

Expected results:
No traceback, content of /etc/pki copied into the "target userspace", possibly a check similar to the workaround I suggested (see below).

Additional info:
* I'm unable to reproduce this issue with an absolute symlink like this one:
"e097f848.r0 -> /var/lib/candlepin/candlepin-crl.crl" (where the latter doesn't exist)
=> In this case, the upgrade is inhibited with "Upgrade requires links in root directory to be relative"

* Suggested workaround (awaiting for the feedback)
# find /etc/{pki,rhsm} -type l ! -exec test -e {} \; -print | xargs rm -fv