dist/redhat: stop using systemd macros, call systemctl directly

Fedora version of systemd macros does not work correctly on CentOS7,
since CentOS7 does not support "file trigger" feature.
Even after 05d4378, scriptlets on old scylla .rpm and new scylla .rpm is
not completely same.

To fix the issue we need to stop using systemd macros, call systemctl
directly.

Fixes #94

(cherry picked from commit 949cefc251)

dist/redhat/scylla-jmx.spec

@@ -38,14 +38,20 @@ echo
 fi
 
 %post
-%systemd_post scylla-jmx.service
+if [ $1 -eq 1 ] ; then
+    /usr/bin/systemctl preset scylla-jmx.service ||:
+fi
+
 /usr/bin/systemctl daemon-reload ||:
 
 %preun
-%systemd_preun scylla-jmx.service
+if [ $1 -eq 0 ] ; then
+    /usr/bin/systemctl --no-reload disable scylla-jmx.service ||:
+    /usr/bin/systemctl stop scylla-jmx.service ||:
+fi
 
 %postun
-%systemd_postun scylla-jmx.service
+/usr/bin/systemctl daemon-reload ||:
 
 %clean
 rm -rf $RPM_BUILD_ROOT

src/main/java/com/scylladb/jmx/utils/APIBuilder.java

@@ -172,7 +172,7 @@ public class APIBuilder extends MBeanServerBuilder {
                         logger.log(SEVERE, "Unexpected error.", x);
                     }
                 } finally {
-                    lock.writeLock().lock();
+                    lock.writeLock().unlock();
                 }
             }
         }