valgrind: add suppression for bash memory leak

Add suppression for memory leak in bash observerd with bash 4.4.011 on
Arch Linux.
Signed-off-by: NTomáš Golembiovský <tgolembi@redhat.com>

tests/.valgrind.supp

@@ -32,6 +32,17 @@
    ...
    obj:*/bin/bash
 }
+{
+   bashMemoryLeak4
+   Memcheck:Leak
+   match-leak-kinds: definite
+   fun:malloc
+   fun:xmalloc
+   fun:set_default_locale
+   fun:main
+   ...
+   obj:*/bin/bash
+}
 #
 # Failure seen in /usr/lib64/ld-2.15.so
 #