exist? must rely on raising exceptions like in v2

The exist? method in version 2 relied upon purposefully raising
exceptions to indicate that a repository is missing. In v3 we tried to
replace this with a check for scm_dir(.git, .hg etc) instead. However we
now realize that exist? needs also to work for remote urls. So we are
reverting back to the ohloh_scm v2 logic:

https://github.com/blackducksoftware/ohloh_scm/blob/v2.5.1/lib/ohloh_scm/adapters/git/misc.rb#L7

Author: notalex

lib/ohloh_scm/status.rb

@@ -12,9 +12,10 @@ def initialize(core)
     end
 
     def exist?
-      return unless scm_dir_exist?
-
       !activity.head_token.to_s.empty?
+    rescue RuntimeError
+      logger.debug { $ERROR_INFO.inspect }
+      false
     end
 
     def scm_dir_exist?

spec/ohloh_scm/bzr/scm_spec.rb

@@ -7,9 +7,10 @@
     with_bzr_repository('bzr') do |src|
       tmpdir do |dest_dir|
         core = OhlohScm::Factory.get_core(scm_type: :bzr, url: dest_dir)
-        refute core.status.exist?
+        refute core.status.scm_dir_exist?
 
         core.scm.pull(src.scm, TestCallback.new)
+        assert core.status.scm_dir_exist?
         assert core.status.exist?
       end
     end

spec/ohloh_scm/git/scm_spec.rb

@@ -5,9 +5,10 @@
     with_git_repository('git') do |src_core|
       tmpdir do |dest_dir|
         core = OhlohScm::Factory.get_core(scm_type: :git, url: dest_dir)
-        refute core.status.exist?
+        refute core.status.scm_dir_exist?
 
         core.scm.pull(src_core.scm, TestCallback.new)
+        assert core.status.scm_dir_exist?
         assert core.status.exist?
       end
     end
@@ -19,7 +20,7 @@
     with_git_repository('git_with_multiple_branch', 'test') do |src_core|
       tmpdir do |dest_dir|
         core = OhlohScm::Factory.get_core(scm_type: :git, url: dest_dir, branch_name: 'test')
-        refute core.status.exist?
+        refute core.status.scm_dir_exist?
         core.scm.pull(src_core.scm, TestCallback.new)
 
         remote_master_branch_sha = `cd #{dest_dir} && git rev-parse origin/master`
@@ -36,8 +37,9 @@
     with_cvs_repository('cvs', 'simple') do |src_core|
       tmpdir do |dest_dir|
         core = OhlohScm::Factory.get_core(scm_type: :git, url: dest_dir)
-        refute core.status.exist?
+        refute core.status.scm_dir_exist?
         core.scm.pull(src_core.scm, TestCallback.new)
+        assert core.status.scm_dir_exist?
         assert core.status.exist?
 
         dest_commits = core.activity.commits