Fix test failure on Darwin

Apparently our DBD::SQLite links against /usr/lib/libsqlite3.dylib,
which is an old version that doesn't respect foreign key constraints.
So manifests/cache.sqlite doesn't get updated properly when a manifest
disappears.  We should fix our DBD::SQLite, but in the meantime this
will fix the test.

http://hydra.nixos.org/build/3017959

tests/binary-cache.sh

@@ -1,6 +1,7 @@
 source common.sh
 
 clearStore
+clearManifests
 
 # Create the binary cache.
 cacheDir=$TEST_ROOT/binary-cache

tests/nix-pull.sh

@@ -28,6 +28,6 @@ cat $outPath/input-2/bar
 
 # Check that the derivers are set properly.
 test $(nix-store -q --deriver "$outPath") = "$drvPath"
-nix-store -q --deriver $(readLink $outPath/input-2) | grep -q -- "-input-2.drv" 
+nix-store -q --deriver $(readLink $outPath/input-2) | grep -q -- "-input-2.drv"
 
 clearManifests