Fix: Missing value error in match-ldap-to-info

Fix: Missing value error in match-ldap-to-info

The code unconditionally tried to remove 'lfservices_releng' from
the user list, causing ValueError when it doesn't exist in the LDAP
group (common in production environments).

Now checks if the user exists before attempting removal.
This was causing info-merge-master jobs to fail.
Fixes: ValueError: list.remove(x): x not in list

Issue: RELENG-5882
Change-Id: I3ca95ac1033c4c80e3642e2fcdbe840179134b14
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>