tests/runtestabidb?.sh.in: Use bash shebang

'function x() { ... }' is a bashism, but /bin/sh may be another shell,
like dash. Just use an explicit /bin/bash shebang as the file relies on
a few other bashisms like 'type'.

    * tests/runtestabidb[1-2].sh.in: Use bash shebang.

Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Dodji Seketeli <dodji@redhat.com>

tests/runtestabidb1.sh.in

@@ -1,4 +1,4 @@
-#! /bin/sh
+#! /bin/bash
 
 # Run an abidb test based on the binaries right here
 

tests/runtestabidb2.sh.in

@@ -1,4 +1,4 @@
-#! /bin/sh
+#! /bin/bash
 
 # Run an abidb test based on the binaries right here