channel filters don't work wit PVA

[Dirk Zimoch]

When using pvget with filters, only the number of elements is adjusted but not the data.
It works with Channel Access.

Example record:

record (aai, "TEST") {
field(FTVL, "SHORT")
field(NELM, "10")
field(INP, [9,8,7,6,5,4,3,2,1])
field(PINI, "YES")
info(test, "Hello World")
}

$ caget TEST TEST.{arr:{s:5}} TEST.{arr:{i:2}} 'TEST.{info:{n:"test"}}'
TEST 10 9 8 7 6 5 4 3 2 1 0
TEST.{arr:{s:5}} 5 4 3 2 1 0
TEST.{arr:{i:2}} 5 9 7 5 3 1
TEST.{info:{n:"test"}} Hello World

$ pvget TEST TEST.{arr:{s:5}} TEST.{arr:{i:2}} 'TEST.{info:{n:"test"}}'
TEST 2021-03-12 10:23:15.524 [9,8,7,6,5,4,3,2,1]
TEST.{arr:{s:5}} 2021-03-12 10:23:15.524 [9,8,7,6,5]
TEST.{arr:{i:2}} 2021-03-12 10:23:15.524 [9,8,7,6,5]
TEST.{info:{n:"test"}} 2021-03-12 10:23:15.524 9

[mdavidsaver (mdavidsaver)]

Transfer to https://github.com/epics-base/pva2pva/issues/41