Show more useful message if mya host not found

[slominskir]

Currently, when a mya host isn't found you'll get:

And logs show something like:

11-Apr-2023 17:34:59.002 SEVERE [https-jsse-nio-443-exec-50] org.jlab.myquery.IntervalController.doGet Unable to service request
        java.sql.SQLException: Unable to obtain DataSource for: opsmya14
                at org.jlab.mya.nexus.PooledNexus.getConnection(PooledNexus.java:60)
                at org.jlab.mya.nexus.PointService.findFloatEvent(PointService.java:64)
                at org.jlab.mya.nexus.PointService.findEvent(PointService.java:45)
                at org.jlab.mya.nexus.DataNexus.findEvent(DataNexus.java:269)
                at org.jlab.myquery.PointWebService.findEvent(PointWebService.java:32)
                at org.jlab.myquery.IntervalController.doGet(IntervalController.java:124)
                at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:705)
                at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:814)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:223)
                at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:158)
                at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:185)
                at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:158)
                at org.jlab.myquery.CacheAndEncodingFilter.doFilter(CacheAndEncodingFilter.java:64)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:185)
                at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:158)
                at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:177)
                at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
                at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
                at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:119)
                at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
                at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
                at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
                at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
                at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:400)
                at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
                at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:859)
                at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1734)
                at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
                at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
                at java.base/java.lang.Thread.run(Thread.java:833)

[slominskir]

Related: #3