Ticket #48406 - Avoid self deadlock by PR_Lock(conn->c_mutex)
    
    Description:  Fixing ticket 48338 introduced a self deadlock.
    To avoid the self deadlock, tried to remove PR_Lock(conn->c_mutex)
    which looked harmless, but it introduced a crash by memory corruption.
    
    This patch replaces PR_Lock/Unlock with PR_EnterMonitor/ExitMonitor,
    respectively.
    
    https://fedorahosted.org/389/ticket/48406
    
    Reviewed by rmeggins@redhat.com, lkrispen@redhat.com, and wibrown@redhat.com.
    Thank you, Rich, Ludwig and William!
    
    (cherry picked from commit f25f804a8bce83b3790e7045dfc03230d7ece1af)
    (cherry picked from commit 84da7d05ddc5a963b0d025df08f38a6ccd7d90d2)
    (cherry picked from commit ad08d1fa7c258bb99cd64a4de570035d82e6a492)
    (cherry picked from commit f69d19a351a34313c5f45499718c892a9bb3b42a)
    (cherry picked from commit 5c89312cdfe484e7b8e4cf32427d7576aa4ba2ac)