tests: bump maxCacheFds to 3

As the dirCache now has 3 entries, the tests should accept
up to 3 extra fds without declaring an fd leak.

internal/fusefrontend/dircache.go

@@ -14,6 +14,8 @@ import (
 const (
 	// Number of entries in the dirCache. Three entries work well for two
 	// (probably also three) parallel tar extracts (hit rate around 92%).
+	// Keen in sync with test_helpers.maxCacheFds !
+	// TODO: How to share this constant without causing in import cycle?
 	dirCacheSize = 3
 	// Enable Lookup/Store/Clear debug messages
 	enableDebugMessages = false

tests/test_helpers/mount_unmount.go

@@ -123,7 +123,9 @@ func UnmountPanic(dir string) {
 }
 
 // gocryptfs may hold up to maxCacheFds open for caching
-const maxCacheFds = 1
+// Keen in sync with fusefrontend.dirCacheSize
+// TODO: How to share this constant without causing in import cycle?!
+const maxCacheFds = 3
 
 // UnmountErr tries to unmount "dir", retrying 10 times, and returns the
 // resulting error.