Update Debian package maintainer scripts

contrib/DEBIAN/postinst

@@ -2,8 +2,9 @@
 # postinst script for zcash
 #
 # see: dh_installdeb(1)
+
 set -e
-set -x
+
 # summary of how this script can be called:
 #        * <postinst> `configure' <most-recently-configured-version>
 #        * <old-postinst> `abort-upgrade' <new version>
@@ -13,9 +14,10 @@ set -x
 #        * <deconfigured's-postinst> `abort-deconfigure' `in-favour'
 #          <failed-install-package> <version> `removing'
 #          <conflicting-package> <version>
-# for details, see http://www.debian.org/doc/debian-policy/ or
+# for details, see https://www.debian.org/doc/debian-policy/ or
 # the debian-policy package
 
+
 case "$1" in
     configure)
     ;;

contrib/DEBIAN/postrm

@@ -4,7 +4,7 @@
 # see: dh_installdeb(1)
 
 set -e
-#set -x
+
 # summary of how this script can be called:
 #        * <postrm> `remove'
 #        * <postrm> `purge'
@@ -15,18 +15,12 @@ set -e
 #        * <new-postrm> `abort-upgrade' <old-version>
 #        * <disappearer's-postrm> `disappear' <overwriter>
 #          <overwriter-version>
-# for details, see http://www.debian.org/doc/debian-policy/ or
+# for details, see https://www.debian.org/doc/debian-policy/ or
 # the debian-policy package
-. /usr/share/debconf/confmodule
-
-case "$1" in
-    upgrade|failed-upgrade)
-    ;;
 
-    remove|abort-install|abort-upgrade|disappear)
-    ;;
 
-    purge)
+case "$1" in
+    purge|remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
     ;;
 
     *)

contrib/DEBIAN/preinst

@@ -4,20 +4,18 @@
 # see: dh_installdeb(1)
 
 set -e
-#set -x
+
 # summary of how this script can be called:
 #        * <new-preinst> `install'
 #        * <new-preinst> `install' <old-version>
 #        * <new-preinst> `upgrade' <old-version>
 #        * <old-preinst> `abort-upgrade' <new-version>
-# for details, see http://www.debian.org/doc/debian-policy/ or
+# for details, see https://www.debian.org/doc/debian-policy/ or
 # the debian-policy package
 
-case "$1" in
-    install)
-   ;;
 
-    upgrade)
+case "$1" in
+    install|upgrade)
     ;;
 
     abort-upgrade)

contrib/DEBIAN/prerm

@@ -13,15 +13,12 @@ set -e
 #        * <deconfigured's-prerm> `deconfigure' `in-favour'
 #          <package-being-installed> <version> `removing'
 #          <conflicting-package> <version>
-# for details, see http://www.debian.org/doc/debian-policy/ or
+# for details, see https://www.debian.org/doc/debian-policy/ or
 # the debian-policy package
 
 
 case "$1" in
-    remove|deconfigure)
-    ;;
-
-    upgrade)
+    remove|upgrade|deconfigure)
     ;;
 
     failed-upgrade)