Fix a typo that broke this module against x64

[SeeRM rapid7#7747]

Author: egypt

modules/exploits/multi/http/jboss_maindeployer.rb

@@ -350,7 +350,7 @@ def detect_architecture(res)
 			arch = $1
 			if (arch =~ /(x86|i386|i686)/i)
 				return ARCH_X86
-			elsif (os =~ /(x86_64|amd64)/i)
+			elsif (arch =~ /(x86_64|amd64)/i)
 				return ARCH_X86
 			end
 		end