libvlc_event_*: fix locking (cherry picked from commit 13b7d257de1eced08708034186e290c0a5f5628a)
libvlc_event_*: fix locking
(cherry picked from commit 13b7d257de1eced08708034186e290c0a5f5628a)

Reverted change to libvlc_event_manger_release().

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