IMPALA-1830: Fix impala-config.sh for non-bash shells
IMPALA-1830: Fix impala-config.sh for non-bash shells

impala-config.sh had three bugs that are fixed with this patch:

  1) Not finding the postgres driver will return from the script, not
  exit the shell.

  2) HADOOP_CLASSPATH uses a corect wildcard path specifier and does not
  rely on shell expansion anymore.

  3) IMPALA_HOME is set correctly even if BASH_SOURCE is not available
  for ZSH shells.

Change-Id: Ifbcf62c643cade43a9007f9bb780fc650760df0e
Reviewed-on: http://gerrit.cloudera.org:8080/407
Reviewed-by: Casey Ching <77bc9a9984e6786c5799d7a71768cf023120ef76@cloudera.com>
Tested-by: Internal Jenkins

ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC