I have Jenkins server running on a MacMini and no matter what, m2e-core-tests time out every time.
Here's what a threaddump gives me : 
"main" prio=5 tid=0x00007faef380a000 nid=0x507 runnable [0x00007fff56d30000]
   java.lang.Thread.State: RUNNABLE
	at java.net.SocketInputStream.socketRead0(Native Method)
	at java.net.SocketInputStream.read(SocketInputStream.java:152)
	at java.net.SocketInputStream.read(SocketInputStream.java:122)
	at com.squareup.okhttp.internal.okio.Okio$2.read(Okio.java:113)
	at com.squareup.okhttp.internal.okio.RealBufferedSource.read(RealBufferedSource.java:48)
	at com.squareup.okhttp.internal.http.HttpConnection$FixedLengthSource.read(HttpConnection.java:417)
	at com.squareup.okhttp.internal.okio.RealBufferedSource$1.read(RealBufferedSource.java:168)
	at java.io.InputStream.read(InputStream.java:101)
	at org.eclipse.m2e.core.internal.index.nexus.AetherClientResourceFetcher.retrieve(AetherClientResourceFetcher.java:87)
	at org.apache.maven.index.updater.AbstractResourceFetcher.retrieve(AbstractResourceFetcher.java:35)
	at org.apache.maven.index.updater.DefaultIndexUpdater$LocalCacheIndexAdaptor.setIndexFile(DefaultIndexUpdater.java:700)
	at org.apache.maven.index.updater.DefaultIndexUpdater.fetchAndUpdateIndex(DefaultIndexUpdater.java:829)
	at org.apache.maven.index.updater.DefaultIndexUpdater.fetchAndUpdateIndex(DefaultIndexUpdater.java:135)
	at org.eclipse.m2e.core.internal.index.nexus.NexusIndexManager.updateRemoteIndex(NexusIndexManager.java:1127)
	at org.eclipse.m2e.core.internal.index.nexus.NexusIndexManager.updateIndex(NexusIndexManager.java:1087)
	- locked <0x00000007f0cf4f00> (a java.lang.Object)
	at org.eclipse.m2e.core.internal.index.nexus.NexusIndex.updateIndex(NexusIndex.java:145)
	at org.eclipse.m2e.tests.internal.index.NexusIndexManagerSearchTest.updateRepo(NexusIndexManagerSearchTest.java:81)
	at org.eclipse.m2e.tests.internal.index.NexusIndexManagerSearchTest.setUp(NexusIndexManagerSearchTest.java:55)