tests/acceptance/ppc_prep_40p: Use mirror for ftp.software.ibm.com

To avoid regular failures on Travis-CI with ftp.software.ibm.com,
use a mirror.

Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Tested-by: Willian Rampazzo <willianr@gmail.com>
Reviewed-by: Willian Rampazzo <willianr@gmail.com>
Message-Id: <20200403172919.24621-4-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

tests/acceptance/ppc_prep_40p.py

@@ -30,7 +30,8 @@ class IbmPrep40pMachine(Test):
         :avocado: tags=machine:40p
         :avocado: tags=slowness:high
         """
-        bios_url = ('ftp://ftp.boulder.ibm.com/rs6000/firmware/'
+        bios_url = ('http://ftpmirror.your.org/pub/misc/'
+                    'ftp.software.ibm.com/rs6000/firmware/'
                     '7020-40p/P12H0456.IMG')
         bios_hash = '1775face4e6dc27f3a6ed955ef6eb331bf817f03'
         bios_path = self.fetch_asset(bios_url, asset_hash=bios_hash)