git: add tests/server/disabled to .gitignore

Closes #4441
diff --git a/tests/server/.gitignore b/tests/server/.gitignore
index d410f5e..94329f7 100644
--- a/tests/server/.gitignore
+++ b/tests/server/.gitignore
@@ -6,3 +6,4 @@
 sws
 tftpd
 socksd
+disabled