mountd(8): parsecred(): Re-order operations for clarity
    
    No functional change (intended).
    
    Reviewed by:    rmacklem (older version)
    Approved by:    markj (mentor)
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D47015
    
    (cherry picked from commit a20d50245f280be404cb8e3b5c9d570ded9594b9)