Made login failure message wording clearer regarding max user sessions.

src/main/resources/META-INF/xnat/preferences/site-config.properties

@@ -32,7 +32,7 @@ UI.show-left-bar-search=true
 UI.show-left-bar-browse=true
 UI.show-manage-files=true
 UI.allow-non-admin-project-creation=true
-UI.login_failure_message=Your login attempt failed because the username and password combination you provided was invalid or the site is currently at the maximum number of user sessions. After %d failed login attempts, your user account will be locked. If you believe your account is currently locked, you can:<ul><li>Unlock it by resetting your password</li><li>Wait one hour for it to unlock automatically</li></ul>
+UI.login_failure_message=Your login attempt failed because the username and password combination you provided was invalid or your user already has the maximum number of user sessions open. After %d failed login attempts, your user account will be locked. If you believe your account is currently locked, you can:<ul><li>Unlock it by resetting your password</li><li>Wait one hour for it to unlock automatically</li></ul>
 
 # Indicates whether access to the list of system users should be restricted to site administrators only.
 restrictUserListAccessToAdmins=false