Update adapter-config.xml

Fix some minor typos in the json, Otherwise it is invalid.

Also deploying in the keycloak 1.0.1 appliance, the line

"cors-allowed-methods" : [ "POST", "PUT", "DELETE", "GET" ],

makes parsing fail with 

11:19:10,121 ERROR [org.jboss.as.controller.management-operation] (DeploymentScanner-threads - 1) JBAS014613: Operation ("full-replace-deployment") failed - address: ([]) - failure description: {"JBAS014671: Failed services" => {"jboss.undertow.deployment.default-server.default-host./rhq-metrics" => "org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./rhq-metrics: Failed to start service
    Caused by: java.lang.RuntimeException: org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
 at [Source: java.io.BufferedInputStream@1605c2fe; line: 9, column: 24] (through reference chain: org.keycloak.representations.adapters.config.AdapterConfig[\"cors-allowed-methods\"])
    Caused by: org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
 at [Source: java.io.BufferedInputStream@1605c2fe; line: 9, column: 24] (through reference chain: org.keycloak.representations.adapters.config.AdapterConfig[\"cors-allowed-methods\"])"}}
Merge pull request #744 from pilhuhn/patch-1

Update adapter-config.xml
Possible NPE in MemUserSessionProvider.getUserSessions