seastar-addr2line: relax the backtrace matching

Allow an arbitrary prefix on the line containing an address as the last
word. This allows for piping journalctl output through seastar-addr2line
as journalctl entries have a date and time as well as other stuff as a
prefix on each line.

scripts/seastar-addr2line

@@ -26,7 +26,7 @@ import subprocess
 
 
 class BacktraceResolver(object):
-    object_address_re = re.compile('^\W*(((/[^/]+)+)\+)?(0x[0-9a-f]+)\W*$')
+    object_address_re = re.compile('^.* (((/[^/]+)+)\+)?(0x[0-9a-f]+)\W*$')
 
     def __init__(self, executable, before_lines):
         self._executable = executable