style(spotbugs): Return more specific interface

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

Author: AndyScherzinger

library/src/main/java/com/owncloud/android/lib/common/network/AdvancedX509KeyManager.java

@@ -287,8 +287,8 @@ private void removeKeyChain(AKMAlias filter) throws IllegalArgumentException {
     * @param filter AKMAlias object used as filter
     * @return all aliases from KEYCHAIN_ALIASES which satisfy alias.matches(filter)
     */
-   private static <T> Collection<String> filterAliases(Collection<T> aliases, AKMAlias filter) {
-      Collection<String> filtered = new LinkedList<>();
+   private static <T> LinkedList<String> filterAliases(Collection<T> aliases, AKMAlias filter) {
+       LinkedList<String> filtered = new LinkedList<>();
       for (Object alias : aliases) {
          if (new AKMAlias(alias.toString()).matches(filter)) {
             filtered.add(((String) alias));
@@ -308,7 +308,7 @@ private static <T> Collection<String> filterAliases(Collection<T> aliases, AKMAl
    private @NonNull String[] getAliases(Set<KeyType> keyTypes, Principal[] issuers, String hostname, Integer port) {
       // Check keychain aliases
       AKMAlias filter = new AKMAlias(KEYCHAIN, null, hostname, port);
-      List<String> validAliases = new LinkedList<>(filterAliases(sharedPreferences.getStringSet(KEYCHAIN_ALIASES, new HashSet<>()), filter));
+      List<String> validAliases = filterAliases(sharedPreferences.getStringSet(KEYCHAIN_ALIASES, new HashSet<>()), filter);
 
       Log_OC.d(TAG, "getAliases(keyTypes=" + (keyTypes != null ? Arrays.toString(keyTypes.toArray()) : null)
               + ", issuers=" + Arrays.toString(issuers)