commitpkg: Fix commit message

Move the message template before the if block. We moved this to the else
branch in commit aaa68e49

 which lead to
"msgtemplate" being unset if one specifies a commit message on the
command line, thus stripping the "upgpkg:" part.

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>