scripts: update default heap and mempry sizes

Motivation:
By default dcache provides very conservative heap and direct memory
sizes, namely 512m. Many sites have adjusted the heap size, but usually
keep the direct memory size as-is. The recent nfs changes require the
direct memory to at least 3% of the heap size. s direct memory shared
by xroot mover pools have hard times to serve the data and fail with
OOME.

Modification:
Bumo default heap and direct memory sizes to 2gb.

Result:
No OOME during pool operation.

Acked-by: Albert Rossi
Target: master, 9.1
Require-book: no
Require-notes: yes

skel/share/defaults/dcache.properties

@@ -112,10 +112,10 @@ dcache.log.resilience.max-history=30
 (not-for-services)dcache.restart.file=${dcache.restart.dir}/.dcache-stop.${dcache.domain.name}
 
 # Java maximum heap size
-(not-for-services)dcache.java.memory.heap=512m
+(not-for-services)dcache.java.memory.heap=2048m
 
 # Java maximum direct buffer size
-(not-for-services)dcache.java.memory.direct=512m
+(not-for-services)dcache.java.memory.direct=2048m
 
 # Directory where to store heapdumps
 (not-for-services)dcache.java.oom.location=${dcache.log.dir}