Consider removing synchronization on indices

[sarthakn7]

indices in GlobalState is synchronized in the getIndex method:

nrtsearch/src/main/java/com/yelp/nrtsearch/server/luceneserver/GlobalState.java

Line 234 in 6b21669

synchronized (indices) {

This method is called in a lot of places (via another getIndex method) and we should consider removing the synchronization. The indices variable is already a concurrent hashmap.