Land #18506, Fix stability issue for f5 2023-46747

This PR fixes a statbility issue with the
f5_bigip_tmui_rce_cve_2023_46747 module. Prior to this fix
occasionally the module would fail on login as things were
running too quickly, the module now retrys loging in.

modules/exploits/linux/http/f5_bigip_tmui_rce_cve_2023_46747.rb

@@ -103,8 +103,11 @@ def exploit
       report_hash('admin', hash)
     end
 
-    res = bigip_api_shared_login
-    fail_with(Failure::UnexpectedReply, 'Failed to login.') unless res&.code == 200
+    logged_in = retry_until_truthy(timeout: 30) do
+      res = bigip_api_shared_login
+      res&.code == 200
+    end
+    fail_with(Failure::UnexpectedReply, 'Failed to login.') unless logged_in
 
     token = res.get_json_document.dig('token', 'token')
     fail_with(Failure::UnexpectedReply, 'Failed to obtain a login token.') if token.blank?