```visual_metrics.py: silence some warnings.

Change-Id: Id0e78d0fde3498d07395c51aa1269f8ca7a7cd88
```
```diff --git a/scripts/visual_metrics.py b/scripts/visual_metrics.py
index 4a67b23..7a9ba9d 100755
--- a/scripts/visual_metrics.py
+++ b/scripts/visual_metrics.py
```
```@@ -23,6 +23,9 @@
from os.path import basename
from os.path import splitext

+warnings.simplefilter('ignore', numpy.RankWarning)
+warnings.simplefilter('ignore', RuntimeWarning)
+
def bdsnr(metric_set1, metric_set2):
"""
BJONTEGAARD    Bjontegaard metric calculation
@@ -46,11 +49,10 @@
psnr1 = [100.0 if x == float('inf') else x for x in psnr1]
psnr2 = [100.0 if x == float('inf') else x for x in psnr2]

-
-  log_rate1 = map(lambda x: math.log(x), rate1)
-  log_rate2 = map(lambda x: math.log(x), rate2)
-
try:
+    log_rate1 = map(lambda x: math.log(x), rate1)
+    log_rate2 = map(lambda x: math.log(x), rate2)
+
# Best cubic poly fit for graph represented by log_ratex, psrn_x.
p1 = numpy.polyfit(log_rate1, psnr1, 3)
p2 = numpy.polyfit(log_rate2, psnr2, 3)
@@ -98,10 +100,10 @@
psnr1 = [100.0 if x == float('inf') else x for x in psnr1]
psnr2 = [100.0 if x == float('inf') else x for x in psnr2]

-  log_rate1 = map(lambda x: math.log(x), rate1)
-  log_rate2 = map(lambda x: math.log(x), rate2)
-
try:
+    log_rate1 = map(lambda x: math.log(x), rate1)
+    log_rate2 = map(lambda x: math.log(x), rate2)
+
# Best cubic poly fit for graph represented by log_ratex, psrn_x.
p1 = numpy.polyfit(psnr1, log_rate1, 3)
p2 = numpy.polyfit(psnr2, log_rate2, 3)
```