Description of problem:
Getting the following error when trying to upgrade all packages(dnf upgrade) for a RHEL 8 client using katello-agent:

2020-04-30T13:20:14Z DDEBUG timer: sack setup: 2314 ms
2020-04-30T13:20:14Z DEBUG Completion plugin: Generating completion cache...
2020-04-30T13:20:14Z DEBUG Completion plugin: Generating completion cache...
2020-04-30T13:20:14Z DDEBUG Getting group metadata
2020-04-30T13:20:14Z DDEBUG Adding group file from repository: rhel-8-for-x86_64-appstream-rpms
2020-04-30T13:20:14Z DDEBUG Adding group file from repository: rhel-8-for-x86_64-baseos-rpms
2020-04-30T13:20:15Z DDEBUG Adding group file from repository: satellite-tools-6.6-for-rhel-8-x86_64-rpms
2020-04-30T13:20:15Z DDEBUG timer: loading comps: 72 ms
2020-04-30T13:20:15Z DEBUG Completion plugin: Generating completion cache...
2020-04-30T13:20:15Z CRITICAL Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/dnf/plugin.py", line 104, in _caller
    getattr(plugin, method)()
  File "/usr/lib/python3.6/site-packages/dnf-plugins/product-id.py", line 59, in transaction
    if len(self.base.transaction) == 0:
TypeError: object of type 'NoneType' has no len()


Seems like there is no transaction ran when calling update without patterns:

In "/usr/lib/python3.6/site-packages/katello/agent/pulp/libdnf.py"

    def update(self, patterns=(), advisories=()):
            <snip>
            if patterns:   <================ This condition is skipping the upgrade when no patterns are provided.
                lib.upgrade(patterns)

            if self.commit:
                lib.do_transaction()


I think it is the regression of the following fix:

https://bugzilla.redhat.com/show_bug.cgi?id=1713417
https://github.com/Katello/katello-host-tools/pull/98


Steps to Reproduce:
1. Go to Web UI -> Hosts -> Content Hosts -> choose a RHEL 8 client -> Packages -> Applicable -> Click "Update All Packages"
2. ssh to the RHEL 8 client, run "tail -f /var/log/dnf.log" to observe the error.


Actual results:
No packages are updated

Expected results:
All packages are updated