KAFKA-4964; Use correct keystore/trustore name in documentation

Author: shuguo zheng <zheng.shuguo@zte.com.cn>

Reviewers: Ismael Juma <ismael@juma.me.uk>

Closes #2749 from zhengsg/local

docs/security.html

@@ -137,10 +137,10 @@
 
             Following SSL configs are needed on the broker side
             <pre>
-            ssl.keystore.location=/var/private/ssl/kafka.server.keystore.jks
+            ssl.keystore.location=/var/private/ssl/server.keystore.jks
             ssl.keystore.password=test1234
             ssl.key.password=test1234
-            ssl.truststore.location=/var/private/ssl/kafka.server.truststore.jks
+            ssl.truststore.location=/var/private/ssl/server.truststore.jks
             ssl.truststore.password=test1234</pre>
 
             Note: ssl.truststore.password is technically optional but highly recommended. If a password is not set access to the truststore is still available, but integrity checking is disabled.
@@ -191,17 +191,17 @@
             If client authentication is not required in the broker, then the following is a minimal configuration example:
             <pre>
             security.protocol=SSL
-            ssl.truststore.location=/var/private/ssl/kafka.client.truststore.jks
+            ssl.truststore.location=/var/private/ssl/client.truststore.jks
             ssl.truststore.password=test1234</pre>
 
             Note: ssl.truststore.password is technically optional but highly recommended. If a password is not set access to the truststore is still available, but integrity checking is disabled.
 
             If client authentication is required, then a keystore must be created like in step 1 and the following must also be configured:
             <pre>
-            ssl.keystore.location=/var/private/ssl/kafka.client.keystore.jks
+            ssl.keystore.location=/var/private/ssl/client.keystore.jks
             ssl.keystore.password=test1234
             ssl.key.password=test1234</pre>
-
+			
             Other configuration settings that may also be needed depending on our requirements and the broker configuration:
                 <ol>
                     <li>ssl.provider (Optional). The name of the security provider used for SSL connections. Default value is the default security provider of the JVM.</li>