Since working copy upgrades from 1.7 to 1.8 are now explicit, instead of
implicit some wc_db apis can now return a working copy upgrade required error.

Make sure the working copy upgrade code doesn't interpret an error from
the sqlite upgrade code as a trigger to try upgrading from entries.


* subversion/libsvn_wc/wc_db.c
  (svn_wc__db_bump_format): Wrap SVN_ERR_WC_UPGRADE_REQUIRED errors from
    the sqlite upgrade code, to avoid falling in the entries code inside
    svn_wc_upgrade.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1439813 13f79535-47bb-0310-9956-ffa450edef68