task/internal/__init__.py: improve core program extraction

task/internal/__init__.py: improve core program extraction

Problem:
The previous technique for extracting the program name
of the coredump file doesn't deal with the case
where there is no white space after program name
e.g.,

``SVR4-style, from 'ceph_test_rados_api_io', real uid: 1000``

here we will get an error when we reach the part where we

``remote.sh(['which', dump_program]).rstrip()``.

Solution:

Use regex to extract first occurence of the word that
is in the format ``from '<word>'``.

Signed-off-by: Kamoltat Sirivadhna <ksirivad@redhat.com>