adjust to qt_plugin.prf changes

DESTDIR and INSTALLS+=target are set up automatically now. note that in
the qmediaserviceprovider test we must override that.
also, TARGET munging is done automatically.

Change-Id: Ida5d5601e22b099134d1ec07ace713e0d0986bd6
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/plugins/audiocapture/audiocapture.pro

@@ -1,9 +1,8 @@
 TARGET = qtmedia_audioengine
 QT += multimedia-private
-PLUGIN_TYPE=mediaservice
 
+PLUGIN_TYPE=mediaservice
 load(qt_plugin)
-DESTDIR = $$QT.multimedia.plugins/$${PLUGIN_TYPE}
 
 HEADERS += audioencodercontrol.h \
     audiocontainercontrol.h \
@@ -23,8 +22,5 @@ SOURCES += audioencodercontrol.cpp \
     audiocapturesession.cpp \
     audiocaptureprobecontrol.cpp
 
-target.path += $$[QT_INSTALL_PLUGINS]/$${PLUGIN_TYPE}
-INSTALLS += target
-
 OTHER_FILES += \
     audiocapture.json