tests: rm pkgcache.bin in 719263 test

As testcases are running really fast it can happen that files which are
changed in reality are considered unchanged as the modify time isn't
changed. What we could do is disable those caches by default, but some
tests actually depend on those and deriving too much from the default by
default (pun intended) is not a good idea for tests after all.

Git-Dch: Ignore

test/integration/test-bug-719263-print-uris-removes-authentication

@@ -25,6 +25,7 @@ Inst unrelated [1] (2 unstable [all])
 Conf unrelated (2 unstable [all])' aptget install unrelated -s
 	testsuccess aptget install unrelated -y
 	testdpkginstalled unrelated
+	rm -rf rootdir/var/cache/apt/*.bin
 	cp -a rootdir/var/lib/dpkg/status-backup-noact rootdir/var/lib/dpkg/status
 }