tests: optparse: Use --config with the setmaxmem command

The virsh-optparse test broke after commit 6ac402c4 because it
always assumed the max memory limit can be adjusted on a running domain
which used to be the case in the old code.
This is only a hot fix for the CI build. The proper fix here is to
re-write the whole test in a self-test/unit-test manner where we only
test virsh's ability to parse various values, not running actual
commands.
Signed-off-by: NErik Skultety <eskultet@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Acked-by: NPeter Krempa <pkrempa@redhat.com>

tests/virsh-optparse

@@ -219,13 +219,13 @@ test -s out && fail=1
 compare exp-err err || fail=1
 
 # Numeric value with valid suffix
-virsh -q -c $test_url setmaxmem test 42MB >out 2>err || fail=1
+virsh -q -c $test_url setmaxmem test 42MB --config >out 2>err || fail=1
 test -s out && fail=1
 test -s err && fail=1
 
 # Numeric value bigger than INT_MAX. No failure here because
 # scaled numeric values are unsigned long long
-virsh -q -c $test_url setmaxmem test 2147483648 >out 2>err || fail=1
+virsh -q -c $test_url setmaxmem test 2147483648 --config >out 2>err || fail=1
 test -s out && fail=1
 test -s err && fail=1
 
@@ -248,7 +248,7 @@ test -s out && fail=1
 compare exp-err err || fail=1
 
 # Numeric value
-virsh -q -c $test_url setmaxmem test 42 >out 2>err || fail=1
+virsh -q -c $test_url setmaxmem test 42 --config >out 2>err || fail=1
 test -s out && fail=1
 test -s err && fail=1