lib/lkp_pattern.rb: add parentheses for regexp to obtain the matching…

… fragment

In commit dd9da9f, new code was introduced to replace
load_regular_expressions method, but missed to add the surrounding
parentheses, so other code cannot obtain the matching fragment, leading
to many spec failures.

Add the parentheses back to obtain the matching fragment correctly.

== fix issue ==

[    0.861994] sysctl could not get directory: /debug/test_sysctl/mnt/mnt_error -30
----------------

Traceback (most recent call last):
	3: from /lkp/yujie/src/stats/dmesg:107:in `<main>'
	2: from /lkp/yujie/src/stats/dmesg:107:in `each'
	1: from /lkp/yujie/src/stats/dmesg:142:in `block in <main>'
/lkp/yujie/src/lib/dmesg.rb:239:in `analyze_error_id': undefined method `sub' for nil:NilClass (NoMethodError)

Add another spec to ensure the error is correctly captured and parsed.

Fixes: dd9da9f ("lib/lkp_pattern.rb: load pattern by removing line started with # or empty")
Signed-off-by: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Philip Li <philip.li@intel.com>

lib/lkp_pattern.rb

@@ -30,7 +30,7 @@ def regexp
                   .reject(&:empty?)
                   .reject { |line| line.start_with?('#') }
 
-      @regexp = Regexp.new lines.join('|')
+      @regexp = Regexp.new "(#{lines.join('|')})"
     end
 
     def patterns

spec/stats/dmesg/82

@@ -0,0 +1 @@
+[    0.861994] sysctl could not get directory: /debug/test_sysctl/mnt/mnt_error -30

spec/stats/dmesg/82.yaml

@@ -0,0 +1,9 @@
+boot_failures: 1
+
+# sysctl could not get directory:
+sysctl_could_not_get_directory: 1
+message:sysctl_could_not_get_directory: [    0.861994] sysctl could not get directory: /debug/test_sysctl/mnt/mnt_error -30
+pattern:sysctl_could_not_get_directory: sysctl could not get directory:
+
+timestamp:last: 0.861994
+timestamp:sysctl_could_not_get_directory: 0.861994