Fixed integration tests

Author: hierynomus

src/itest/groovy/com/hierynomus/sshj/sftp/FileWriteSpec.groovy

@@ -32,7 +32,7 @@ import static org.codehaus.groovy.runtime.IOGroovyMethods.withCloseable
 class FileWriteSpec extends Specification {
     @Shared
     @ClassRule
-    SshdContainer sshd
+    SshdContainer sshd = new SshdContainer()
 
     def "should append to file (GH issue #390)"() {
         given:

src/itest/groovy/com/hierynomus/sshj/signature/SignatureSpec.groovy

@@ -29,7 +29,7 @@ import spock.lang.Unroll
 class SignatureSpec extends Specification {
     @Shared
     @Container
-    static SshdContainer sshd
+    static SshdContainer sshd = new SshdContainer()
 
     @Unroll
     def "should correctly connect with #sig Signature"() {