Bug 1775184

Description of problem:
With both mirrorlist and baseurl defined in a repo file, if the mirrorlist cannot be found it does not fall back to baseurl.

This worked on previous RHEL major versions (5/6/7)

Version-Release number of selected component (if applicable):
dnf-4.2.7-6.el8.noarch

How reproducible:
Always

Steps to Reproduce:

Create custom repo file, create a mirrorlist that is not available

[RHEL-8-20191106_3]
#BaseOS
name=RHEL-8-20191106_3
#fake mirror list to replicate issue
mirrorlist=http://192.168.122.1:8080/BaseOSXX
enabled=1
baseurl=http://192.168.122.1:8080/BaseOS
gpgcheck=0
repo_gpgcheck=1
gpgkey=http://192.168.122.1:8080/BaseOS/my.key

running yum/dnf commands

# dnf  -v --disablerepo=* --enablerepo=RHEL-8-20191106_3 list
Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, needs-restarting, playground, product-id, repoclosure, repodiff, repograph, repomanage, reposync, uploadprofile
DNF version: 4.2.7
cachedir: /var/cache/dnf
repo: downloading from remote: RHEL-8-20191106_3
error: Status code: 404 for http://192.168.122.1:8080/BaseOSXX (http://192.168.122.1:8080/BaseOSXX).
RHEL-8-20191106_3                                22 kB/s | 195  B     00:00    
Cannot download 'http://192.168.122.1:8080/BaseOSXX': Cannot prepare internal mirrorlist: Status code: 404 for http://192.168.122.1:8080/BaseOSXX.
Failed to download metadata for repo 'RHEL-8-20191106_3'
Error: Failed to download metadata for repo 'RHEL-8-20191106_3'


Actual results:
cannot find mirrorlist so fails to download repo metadata but basurl (which is available) is never tried


Expected results:
Fall back to basurl if mirrorlist is unavailable similar to what happened on previous RHEL releases

behaviour on RHEL7
# yum --disablerepo=* --enablerepo=myrepo list | more
Loaded plugins: boks-protect, changelog, fastestmirror, langpacks, tmprepo,
              : verify, versionlock
Determining fastest mirrors
Could not retrieve mirrorlist http://url/myrepoXX error was
14: HTTP Error 404 - Not Found
 * myrepo
Installed Packages
GeoIP.x86_64                           1.5.0-13.el7             @repo
NetworkManager.x86_64                  1:1.12.0-10.el7_6        @repo
NetworkManager-config-server.noarch    1:1.12.0-10.el7_6        @repo
NetworkManager-libnm.x86_64            1:1.12.0-10.el7_6        @repo


Additional info: