IPA replica/server install does not check for a client

When IPA replica or server is configured it does not check for
possibly installed client. This will cause the installation to
fail in the very end.

This patch adds a check for already configured client and suggests
removing it before server/replica installation.

https://fedorahosted.org/freeipa/ticket/1002

install/tools/ipa-replica-install

@@ -343,6 +343,11 @@ def main():
     if not ipautil.file_exists(filename):
         sys.exit("Replica file %s does not exist" % filename)
 
+    client_fstore = sysrestore.FileStore('/var/lib/ipa-client/sysrestore')
+    if client_fstore.has_files():
+        sys.exit("IPA client is already configured on this system.\n"
+                 + "Please uninstall it first before configuring the replica.")
+
     global sstore
     sstore = sysrestore.StateFile('/var/lib/ipa/sysrestore')