streamfilter/httplive.c: UpdatePlaylist() actually lock segment when updating it.
streamfilter/httplive.c: UpdatePlaylist() actually lock segment when updating it.

When an already existing segment is updated, then make sure it to take the lock.

shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,krichter722/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,krichter722/vlc,krichter722/vlc,krichter722/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc