net: Disable upnp by default

Common sentiment is that the miniupnpc codebase likely contains further
vulnerabilities.

I'd prefer to get rid of the dependency completely, but a compromise for
now is to at least disable it by default.

Github-Pull: #6795
Rebased-From: 21d27ebad5721bc61c62bc72dc3ab3197f9da268

contrib/gitian-descriptors/gitian-linux.yml

@@ -24,7 +24,7 @@ files: []
 script: |
   WRAP_DIR=$HOME/wrapped
   HOSTS="i686-pc-linux-gnu x86_64-unknown-linux-gnu"
-  CONFIGFLAGS="--enable-upnp-default --enable-glibc-back-compat --enable-reduce-exports LDFLAGS=-static-libstdc++"
+  CONFIGFLAGS="--enable-glibc-back-compat --enable-reduce-exports LDFLAGS=-static-libstdc++"
   FAKETIME_HOST_PROGS=""
   FAKETIME_PROGS="date ar ranlib nm strip"
 

contrib/gitian-descriptors/gitian-osx.yml

@@ -27,7 +27,7 @@ files:
 script: |
   WRAP_DIR=$HOME/wrapped
   HOSTS="x86_64-apple-darwin11"
-  CONFIGFLAGS="--enable-upnp-default --enable-reduce-exports GENISOIMAGE=$WRAP_DIR/genisoimage"
+  CONFIGFLAGS="--enable-reduce-exports GENISOIMAGE=$WRAP_DIR/genisoimage"
   FAKETIME_HOST_PROGS=""
   FAKETIME_PROGS="ar ranlib date dmg genisoimage"
 

contrib/gitian-descriptors/gitian-win.yml

@@ -26,7 +26,7 @@ files: []
 script: |
   WRAP_DIR=$HOME/wrapped
   HOSTS="x86_64-w64-mingw32 i686-w64-mingw32"
-  CONFIGFLAGS="--enable-upnp-default --enable-reduce-exports"
+  CONFIGFLAGS="--enable-reduce-exports"
   FAKETIME_HOST_PROGS="g++ ar ranlib nm windres strip"
   FAKETIME_PROGS="date makensis zip"