debian/rules: invoke dh_installinit

Was broken in the package redesign in svn r7578.
lintian integration in Jenkins ftw!

Closes: unstable build https://jenkins.mgm.sipwise.com/job/mediaproxy-ng-binaries/172/

From: Michael Prokop <mprokop@sipwise.com>

debian/rules

@@ -83,6 +83,7 @@ install: build
 	dh_link              -p$@ -P$(b)/$@
 	dh_installdocs       -p$@ -P$(b)/$@
 	dh_installchangelogs -p$@ -P$(b)/$@
+	dh_installinit       -p$@ -P$(b)/$@
 	dh_install           -p$@ -P$(b)/$@
 	dh_strip             -p$@ -P$(b)/$@ --keep-debug
 	dh_compress          -p$@ -P$(b)/$@