[ASTERIXDB-2478][NET] Calculate Buffer Remaining Before Reusing It

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- When recycling a buffer, calculate the buffer remaining before
  releasing it for reuse to prevent other threads from changing
  its remaining.
- Add test case.

Change-Id: Icca3284feae800dd6c37694bdefec3516cd4c506
Reviewed-on: https://asterix-gerrit.ics.uci.edu/3036
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/hyracks-fullstack/hyracks/hyracks-net/pom.xml b/hyracks-fullstack/hyracks/hyracks-net/pom.xml
index 1040e81..4ca20ca 100644
--- a/hyracks-fullstack/hyracks/hyracks-net/pom.xml
+++ b/hyracks-fullstack/hyracks/hyracks-net/pom.xml
@@ -60,5 +60,11 @@
       <artifactId>hyracks-util</artifactId>
       <version>${project.version}</version>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-all</artifactId>
+      <version>2.0.2-beta</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>