ipatests/test_nfs.py: wait before umount

umount calls including in cleanup do not wait.
The test failed once with:
"umount.nfs4: /home: device is busy"
which looks like a leftover open file descriptor.
Add wait periods before umount.

Fixes: https://pagure.io/freeipa/issue/8144
Signed-off-by: François Cami <fcami@redhat.com>
Reviewed-By: Thomas Woerner <twoerner@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipatests/test_integration/test_nfs.py

@@ -39,6 +39,8 @@ class TestNFS(IntegrationTest):
         nfsclt = self.clients[1]
         automntclt = self.clients[2]
 
+        time.sleep(WAIT_AFTER_UNINSTALL)
+
         nfsclt.run_command(["umount", "-a", "-t", "nfs4"])
         nfsclt.run_command(["systemctl", "stop", "rpc-gssd"])
 
@@ -205,6 +207,8 @@ class TestNFS(IntegrationTest):
 
         # TODO leverage users
 
+        time.sleep(WAIT_AFTER_UNINSTALL)
+
         automntclt.run_command(["umount", "-a", "-t", "nfs4"])
 
         result2 = automntclt.run_command([