metadata_scm: Avoid crashing on new svn version layouts

This avoids crashing on newer svn layouts where the entries files
don't contain three lines. If someone wants to fix this to
get the right version on newer subversion checkouts, patches
welcome but this at least stops things crashing.

[YOCTO #5363]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
adt-installer: Switch from svn to tarball release for opkg

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>