snapcraft: use new snapcraft rules to clean up wrapping of executables (#2056)

Snapcraft has an improved mechanism for wrapping python executables.
Remove all the older snapcraft legacy cruft and update for the new
snapcraft tooling.
Signed-off-by: Colin Ian King <colin.king@canonical.com>

snapcraft/Makefile

@@ -29,7 +29,7 @@ all: set_version
 	snapcraft
 
 set_version:
-	cat snapcraft.yaml | sed 's/version: .*/version: $(V)/' > snapcraft-tmp.yaml
+	cat snapcraft.yaml | sed 's/^version: .*/version: $(V)/' > snapcraft-tmp.yaml
 	mv snapcraft-tmp.yaml snapcraft.yaml
 
 install: