replicainstall: Make sure the enrollment state is preserved

During the promote_check phase, the subsequent checks after the machine
is enrolled may cause the installation to abort, hence leaving it
enrolled even though it might not have been prior to the execution of
the ipa-replica-install command.

Make sure that ipa-client-install --uninstall is called on the machine
that has not been enrolled before in case of failure during the
promote_check phase.

https://fedorahosted.org/freeipa/ticket/5529

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/install/server/replicainstall.py

@@ -385,6 +385,34 @@ def common_cleanup(func):
     return decorated
 
 
+def preserve_enrollment_state(func):
+    """
+    Makes sure the machine is unenrollled if the decorated function
+    failed.
+    """
+    def decorated(installer):
+        try:
+            func(installer)
+        except BaseException:
+            if installer._enrollment_performed:
+                uninstall_client()
+            raise
+
+    return decorated
+
+
+def uninstall_client():
+    """
+    Attempts to unenroll the IPA client using the ipa-client-install utility.
+
+    An unsuccessful attempt to uninstall is ignored (no exception raised).
+    """
+
+    print("Removing client side components")
+    ipautil.run([paths.IPA_CLIENT_INSTALL, "--unattended", "--uninstall"],
+                raiseonerr=False)
+
+
 def promote_sssd(host_name):
     sssdconfig = SSSDConfig.SSSDConfig()
     sssdconfig.import_config()
@@ -790,6 +818,8 @@ def ensure_enrolled(installer):
     # Call client install script
     service.print_msg("Configuring client side components")
     try:
+        installer._enrollment_performed = True
+
         args = [paths.IPA_CLIENT_INSTALL, "--unattended"]
         stdin = None
 
@@ -831,9 +861,11 @@ def ensure_enrolled(installer):
                  "ipa-client-install returned: " + str(e))
 
 @common_cleanup
+@preserve_enrollment_state
 def promote_check(installer):
     options = installer
 
+    installer._enrollment_performed = False
     installer._top_dir = tempfile.mkdtemp("ipa")
 
     tasks.check_selinux_status()