Need your assistance to create a F5 redirection rule for /user/login.seam -> /login

As Michael noted, you must be careful with upper/lower case comparisons. For completeness' sake, this ought to work in all cases (no pun intended):

when HTTP_REQUEST {
  if { [string tolower [HTTP::path]] ends_with "/user/login.seam" } {
      HTTP::path [string map -nocase {"/user/login.seam" "/login"} [HTTP::path] ]
  }
}