MetricsInterceptor is doing reflection without privileged blocks

[jmartisk]

... causing issues with metric annotation scanning when SR Metrics is running with security manager enabled

2019-01-10 13:32:29,976 ERROR [io.undertow.request] (default task-1) UT005023: Exception handling request to /: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessDeclaredMembers")
	at java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
	at java.security.AccessController.checkPermission(AccessController.java:884)
	at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
	at java.lang.Class.checkMemberAccess(Class.java:2348)
	at java.lang.Class.getDeclaredMethods(Class.java:1974)
	at io.smallrye.metrics.interceptors.MetricsInterceptor.metrics(MetricsInterceptor.java:66)
(...)