Update glibc version in documentation

Author: Stefan Botez

aws-lambda-java-runtime-interface-client/README.md

@@ -15,7 +15,7 @@ Choose a preferred base image. The Runtime Interface Client is tested on Amazon
 
 * built for x86_64
 * contains Java >= 8
-* contains glibc >= 2.12 or musl
+* contains glibc >= 2.17 or musl
 
 ### Example
 

aws-lambda-java-runtime-interface-client/src/main/jni/Dockerfile.glibc

@@ -1,4 +1,4 @@
-# we use centos 7 to build against glibc 2.12
+# we use centos 7 to build against glibc 2.17
 FROM centos:7
 
 # aws-lambda-cpp requires cmake3, it's available in EPEL

aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/CustomerClassLoaderTest.java

@@ -116,8 +116,10 @@ public void customerClassLoaderFunction() throws IOException {
                     res);
         } catch(Throwable t) {
             // this system property is the name of the charset used when encoding/decoding file paths
-            // exception is expected if it is not set to a UTF variant
-            if (!System.getProperty("sun.jnu.encoding").toLowerCase().contains("utf")){
+            // exception is expected if it is not set to a UTF variant or not set at all
+            String systemEncoding = System.getProperty("sun.jnu.encoding");
+
+            if (systemEncoding != null && !systemEncoding.toLowerCase().contains("utf")){
                 Assertions.assertTrue(t.getMessage().contains("Malformed input or input contains unmappable characters"));
             }
             else {